docs(access policies): Creating Proper Access Policies Guide

[jjoyce0510]

Summary
In this PR, we create an Access Policies guide that is more digestible than what we currently have, including step-by-step instructions on creating policies.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[github-actions]

Unit Test Results (build & test)

597 tests  ±0   593 ✔️ ±0   11m 55s ⏱️ -8s
147 suites ±0       4 💤 ±0 
147 files   ±0       0 ❌ ±0 

Results for commit 57394df. ± Comparison against base commit 5a2bdea.

♻️ This comment has been updated with latest results.

[maggiehays]

@jjoyce0510 Left comments throughout; this is a long read and is a bit confusing to jump between the nitty-gritty details between the policy types. Consider changing the outline to:

About DataHub Access Policies

Move description of & differences between Metadata Policy vs. Platform Policy here

Access Policies Setup, Prerequisites, and Permissions

Using Access Policies

Creating a Metadata Policy

Step 1: Name & Describe
Step 2: Configure Privileges
Step 3: Configure Entity Types/Specific Assets
Step 4: Choose Policy Actors

Creating a Platform Policy

Step 1: Name & Describe
Step 2: Configure Privileges
Step 3: Choose Policy Actors

Updating an Existing Policy

Removing a Policy

Deactivating a Policy

Default Policies

[laulpogan]

@shirshanka with both Maggie and John out we'll need to wait on this one, at least one of the open comments needs domain knowledge/attention

[jjoyce0510]

Addressed the comments - also raised a new PR for this! https://github.com/datahub-project/static-assets/compare/jj--add-policies-images?expand=1