Add User Update Endpoint

[calebbourg]

Description

This PR introduces a pattern for providing partial updates to database tables via our API.
By partial updates I mean that we are able to modify a subset of columns for any given table without having to provide values for the the other columns. The pattern is somewhat based on the pattern for filtering queries as introduced in #102

Note: This new endpoint assumes that the user being updated will always be the current user (as noted inline in comments). At some point we will likely want a user to be able to make updates to another user. We can decide how the code diverges at that point when we know more about how we want that to work.

Changes

• Adds generic update function
• Updates user updating to use new function
• Adds PUT /users update endpoint
• Fixes a small issue with the Rapidoc for login

Testing Strategy

I was able to test partially updating a user in Rapidoc

Coming Up

• Adding New Users
• Updating Coaching Sessions
• Stricter validations