Deprecate pushing loose code from UCM

[ChrisPenner]

Overview

Working with Loose Code (i.e. code outside of a project) on Share is a slower, worse-organized experience than projects.

The plan is to gracefully deprecate Loose Code to help simplify pushing code to Share by only having a single preferred way to do it, and to simplify the implementation of Share as well.

We want to make sure that users still have access to their Share code in the meantime, but know that it's time to move it into projects, so this change will provide a nice message to the user when they try to push loose code to Share:

Users can still pull code from loose-code.

Loose code READMEs have been ported to a new 'bio' field on the Share user and Simon will be swapping over the UI to use that ASAP :)

Implementation notes

• Deletes the implementation of pushing code to Share's loose code, replacing it with a nice deprecation message and instructions on how to move forwards.

Test coverage

Tried it out locally.

Loose ends

After this is deployed and out for a bit I'll remove the implementation from Share as well.

[aryairani]

Oh, I thought the plan was just to migrate/filter UCM's loose code into a project? I think we are ready for that.

Is the goal of this PR then just to block updates to loose code README since you're in the middle of manually converting those and need to block further writes?

[ChrisPenner]

I thought the plan was just to migrate/filter UCM's loose code into a project?

We may choose to do that, but I wouldn't say I necessarily had a plan figured out for it.

I think the biggest thing is that I'd like to start to push people away from loose code towards projects just so whatever we do decide to do is low friction since everyone has already left loose code.

I'd rather not port loose code into projects since those would be really weird projects and likely would cause performance issues in rendering code, computing name lookups, syncing with global defn search, etc.

If we allow users to still pull from loose code they can port it to a proper project at their leisure, if we need to kill loose code for good in the future we can investigate other tacts.