Create an endpoint to update a user's information

[gabriel-flynn]

When a user wants to update something on their profile we need an endpoint that will:

1. Verify that they are the owner of the account that they're trying to update
2. Updates only the fields necessary? (Have to look into whether writes/reads are more costly - assuming Firebase reads are much cheaper than writes. If writing one object counts as one write then we might as well just blindly update)
   • Compare the fields they want to update to what is in their account and only update the fields that are different

[gabriel-flynn]

Firebase docs: https://firebase.google.com/docs/firestore