Creates an App from ghapp-manifest.yaml, pointed at:
| api | https://app.cc0.mtmk.dev |
| webhook | https://app.cc0.mtmk.dev/webhooks/github |
| callback | https://app.cc0.mtmk.dev/auth/callback/login |
| name | cc-dev-2m7k2cll |
Target comes from Ingress in config.local.yaml.
Override with ?base=https://app.cc1.mtmk.dev.