Categorize built-in rules documentation (#347)

* Categorize built-in rules

* Align the indentation

* Fix typo

src/rules/README.md

@@ -3,7 +3,9 @@
 This folder contains the built-in rules for Schemalint.
 While there is value in these, the true benefit is achieved by writing custom rules that enforce the specific architecture that you are aiming for.
 
-## name-casing
+## Naming Conventions
+
+### name-casing
 
 Check that your names are cased correctly. The default setting is `"snake"` (i.e. tables should be named with underscores as word boundaries: `member_profile`).
 The reasoning for this is outlined in the Postgres wiki: [Don't use upper case table or column names ](https://wiki.postgresql.org/wiki/Don't_Do_This#Don.27t_use_upper_case_table_or_column_names).
@@ -18,29 +20,31 @@ At the moment, this rule checks tables, views and columns.
   },
 ```
 
-## prefer-text-to-varchar
+### name-inflection
 
-In Postgres there is no performance penalty on using the `text` type which has no maximum length, so you will generally want to choose that over `varchar`.
-The reasoning for this is outlined in the Postgres wiki: [Don't use varchar(n) by default](https://wiki.postgresql.org/wiki/Don't_Do_This#Don.27t_use_varchar.28n.29_by_default)
+If you want to enforce singular or plural naming for your tables, this rule can enforce it.
+Which one to choose is a matter of great debate but in the end it comes down to personal preference. You can choose `'singular'` (default) or `'plural'`.
 
 ```js
   rules: {
-    'prefer-text-to-varchar': ['error'],
+    'name-inflection': ['error', 'singular'],
   },
 ```
 
-## name-inflection
+## Data Types
 
-If you want to enforce singular or plural naming for your tables, this rule can enforce it.
-Which one to choose is a matter of great debate but in the end it comes down to personal preference. You can choose `'singular'` (default) or `'plural'`.
+### prefer-text-to-varchar
+
+In Postgres there is no performance penalty on using the `text` type which has no maximum length, so you will generally want to choose that over `varchar`.
+The reasoning for this is outlined in the Postgres wiki: [Don't use varchar(n) by default](https://wiki.postgresql.org/wiki/Don't_Do_This#Don.27t_use_varchar.28n.29_by_default)
 
 ```js
   rules: {
-    'name-inflection': ['error', 'singular'],
+    'prefer-text-to-varchar': ['error'],
   },
 ```
 
-## prefer-timestamptz-to-timestamp
+### prefer-timestamptz-to-timestamp
 
 In Postgres when you insert a value into a `timestamptz` column, PostgreSQL converts the `timestamptz` value into a UTC value and stores the UTC value in the table, and when you query `timestamptz`
 from the database, PostgreSQL converts the UTC value back to the time value of the timezone set by the database server, the user, or the current database connection, whereas `timestamp` does not save any
@@ -52,7 +56,7 @@ timezone data. You can learn more here: [Understanding PostgreSQL Timestamp Data
   },
 ```
 
-## prefer-jsonb-to-json
+### prefer-jsonb-to-json
 
 `json` data is stored as a copy of the input text which processing functions need to reparse on each execution. `jsonb` data is stored in a binary format which is faster to process, and also supports indexing.
 
@@ -68,7 +72,7 @@ You can learn more here: [JSON types](https://www.postgresql.org/docs/current/da
   },
 ```
 
-## prefer-identity-to-serial
+### prefer-identity-to-serial
 
 Identity columns are a SQL standard-conforming variant of PostgreSQL's serial columns. They fix a few usability
 issues that serial columns have:
@@ -87,19 +91,21 @@ You can learn more here: [Identity Columns Explained](https://www.2ndquadrant.co
   },
 ```
 
-## require-primary-key
+## Table Structures
 
-Identity tables that do not have a primary key defined. Tables can be ignored by passing the `ignorePattern` rule argument.
+### require-primary-key
+
+Identify tables that do not have a primary key defined. Tables can be ignored by passing the `ignorePattern` rule argument.
 
 ```js
- rules: {
+  rules: {
     'require-primary-key': ['error', {
       ignorePattern: 'information_schema.*'
     }],
   },
 ```
 
-## index-referencing-column
+### index-referencing-column
 
 PostgreSQL does not automatically create an index on the referencing column (not the referenced column) of a foreign key constraint. This rule can enforce that you create an index on the referencing column.
 
@@ -110,45 +116,47 @@ As the official PostgreSQL documentation states, it is not always needed to inde
 You can learn more here: [Foreign Keys](https://www.postgresql.org/docs/current/ddl-constraints.html#DDL-CONSTRAINTS-FK)
 
 ```js
-rules: {
-  'index-referencing-column': ['error'],
-}
+  rules: {
+    'index-referencing-column': ['error'],
+  }
 ```
 
-## reference-actions
+### reference-actions
 
 This rule enforces that foreign key constraints have specific `ON UPDATE` and `ON DELETE` actions. Available actions are: `NO ACTION`, `RESTRICT`, `CASCADE`, `SET NULL`, `SET DEFAULT`. When `onUpdate` or `onDelete` is not specified, the rule allows any action for the unspecified action.
 
 ```js
-rules: {
-  'reference-actions': ['error', {
-    onUpdate: 'NO ACTION',
-    onDelete: 'CASCADE',
-  }],
-}
+  rules: {
+    'reference-actions': ['error', {
+      onUpdate: 'NO ACTION',
+      onDelete: 'CASCADE',
+    }],
+  }
 ```
 
-## row-level-security
+### mandatory-columns
 
-[Row-level security](https://www.postgresql.org/docs/current/ddl-rowsecurity.html) (RLS) is a feature that enables you to control which rows in a table are visible to different users. This rule checks that tables have row-level security enabled. You can also check that it is enforced by setting the `enforced` option to `true`.
+This rule enforces that a table has certain columns. The option is an object, where the key is the column name and the value is the object representing the required properties. Any property of the [TableColumn](https://kristiandupont.github.io/extract-pg-schema/api/extract-pg-schema.tablecolumn.html) object can be used as a required property. For example, you can specify `ordinalPosition` to ensure that the column is in the expected position, but note that PostgreSQL always adds a new column to the very back.
 
 ```js
-rules: {
-    'row-level-security': ['error', {enforced: true}],
-}
+  rules: {
+    'mandatory-columns': ['error', {
+      created_at: {
+        expandedType: 'pg_catalog.timestamptz',
+        isNullable: false,
+      }
+    }],
+  }
 ```
 
-## mandatory-columns
+## Security
 
-This rule enforces that a table has certain columns. The option is an object, where the key is the column name and the value is the object representing the required properties. Any property of the [TableColumn](https://kristiandupont.github.io/extract-pg-schema/api/extract-pg-schema.tablecolumn.html) object can be used as a required property. For example, you can specify `ordinalPosition` to ensure that the column is in the expected position, but note that PostgreSQL always adds a new column to the very back.
+### row-level-security
+
+[Row-level security](https://www.postgresql.org/docs/current/ddl-rowsecurity.html) (RLS) is a feature that enables you to control which rows in a table are visible to different users. This rule checks that tables have row-level security enabled. You can also check that it is enforced by setting the `enforced` option to `true`.
 
 ```js
-rules: {
-  'mandatory-columns': ['error', {
-    created_at: {
-      expandedType: 'pg_catalog.timestamptz',
-      isNullable: false,
-    }
-  }],
-}
+  rules: {
+      'row-level-security': ['error', {enforced: true}],
+  }
 ```