Improve server-side operations API

[sodic]

Closes #1909 using the approach described in the last comment on the issue. Closes #2004.

[!NOTE] I've only implemented the API for AuthUser for now. I think I'll make another issue that deals with adding User to the mix because it's probably not important enough to justify the time it would take.

[!TIP] I recommend generating the files by running wasp start and looking at the SDK. It's much easier to understand what's going on this way. Choose an app with many operations (e.g., waspc/todoApp)

[!WARNING] I love these admonitions and have started overusing them.

Todos:

• [x] Make an issue for supporting User.
• [x] Test thoroughly one more time.
• [x] Update public API table.
• [x] Update docs.
• [x] Update changelog.

[infomiho]

Good job!

It seems like the AuthUser is causing some trouble for us here 😢 they can simply coerce some object like { id: 5 } as AuthUser as an extreme measure?