Description #
This PR adds support to synchub for multiple GitHub accounts. After the first sign-up and connect is finished, users can now go to "Add account" in the profile menu and either sign in with another GitHub user or sign in with the same and then choose another organisation to install the GitHub app in. They then need to verify again as before. However, I made step 2 more convenient by automatically filling in the already signed in ATproto account, so people don't have to reenter. I didn't want to skip step 2 entirely, because I wanted to give users the flexibility to still enter another handle.
This change includes a db migration because we have a new junction table to allow multiple GitHub accounts. So if it is not automated in the Vercel build process, please remember to run pnpm db:migrate 👍
Additionally, I adapted two places where the production GitHub App was hard-coded in the link and replaced it with the env var, so it works nicely locally.