remove (Query): #first and #last shortcuts

BREAKING CHANGE: It is done because primary key can be
an unordable type, e.g. UUID, therefore it would make
no sense to call `#first`

spec/model/class_query_shortcuts_spec.cr

@@ -49,7 +49,7 @@ describe Onyx::SQL::Model::ClassQueryShortcuts do
     end
   end
 
-  {% for m in %w(update delete all one first last) %}
+  {% for m in %w(update delete all one) %}
     describe {{m}} do
       it do
         User.{{m.id}}.should eq Query(User).new.{{m.id}}

src/onyx-sql/query.cr

@@ -10,8 +10,6 @@ module Onyx::SQL
   # * Shortcuts:
   #   * `#one`
   #   * `#all`
-  #   * `#first`
-  #   * `#last`
   #   * `#and`
   #   * `#or`
   #   * `#and_not`
@@ -217,18 +215,6 @@ module Onyx::SQL
       limit(1)
     end
 
-    # Alias of `#order_by(primary_key, :asc).one`. The primary key is determined by the
-    # `Model::Options` `:primary_key` option.
-    def first
-      order_by(primary_key, :asc).one
-    end
-
-    # Alias of `#order_by(primary_key, :desc).one`. The primary key is determined by the
-    # `Model::Options` `:primary_key` option.
-    def last
-      order_by(primary_key, :desc).one
-    end
-
     # Return the SQL representation of this query.
     # Pass `true` to replace `"?"` query arguments with `"$n"`, which would work for PostgreSQL.
     def to_s(index_params = false)
@@ -330,22 +316,5 @@ module Onyx::SQL
     private class ParamIndex
       property value = 0
     end
-
-    protected def primary_key
-      {% begin %}
-        {%
-          options = T.annotation(Model::Options)
-          raise "Onyx::SQL::Model::Options annotation must be defined for #{T}" unless options
-
-          pk = options[:primary_key]
-          raise "Onyx::SQL::Model::Options annotation is missing :primary_key option for #{T}" unless pk
-
-          pk_ivar = T.instance_vars.find { |riv| "@#{riv.name}".id == pk.id }
-          raise "Cannot find primary key field #{pk} for #{T}" unless pk_ivar
-        %}
-
-        {{pk_ivar.name.symbolize}}
-      {% end %}
-    end
   end
 end