Completed collections, posts, and users documentation.

[sandrockcstm]

Problem

As of now, there exists no documentation explaining the database schema of writefreely. This can make administration of an instance more difficult, as well as slows down development efforts that require interaction with the database.

Solution

This merge will add a new page to project documentation that explains each piece of the database schema. To start, only the collections, posts, and users sections are completed, with some placeholder text in other areas. The rest of the documentation can be filled out at a later date as devs and contributors work with these pieces of the database schema (or in one shot if someone is so inclined).

Review

Please check the accuracy of descriptions for each of these attributes. While I spent some time examining the code and doing some tests with my own dev instance, I'm not as familiar with the codebase as would be ideal. Corrections should be made where inaccuracies are found to avoid future confusion in the development process.

I made a decision when I drafted this document to leave headers as placeholders for unfinished sections. While this does create some clutter in the short-term, I believe this will serve as a visual reminder that parts of this document are unfinished and need to be completed. If this is not desired, they can be removed for immediate cleaner documentation.

[thebaer]

Thanks, @sandrockcstm! Great idea to document this, and good strategy with the placeholder text. I've added the missing information and clarified a few things. Going to merge now.