feat(docs): refactor source and sink docs

[kevinhu]

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)

[jjoyce0510]

This is amazing.

[jjoyce0510]

First of all : WOW! This was a huge amount of work to make these docs better. Thank you so much for your efforts! These changes will greatly improve the usability of the ingestion framework.

Now for a summary of comments. Overall it looks great, just a couple suggestions remaining.

I see that you've removed metadata-ingestion README. I do think we still need a top level parent page for

• What is the metadata ingestion framework
• What is a recipe file
• How am I expected to productionize / deploy this?
• Any links to contributing guides etc.

I think we should continue to try to establish conventions for common patterns in each source doc:

• credentials / authentication
• pointing to the correct location of the source system
• and connector-specific options and feature configurations
  It'd be useful to think about ways to highlight these categories in a consistent manner across all source docs!

[jjoyce0510]

LGTM.

Thank you!

[shirshanka]

LGTM. Thanks a lot for this awesome contrib @kevinhu