### What needs to get done The `plugs` and `slots` keys have many keys. A few `plug` keys exist but no `slots` keys are documented or defined in [the project model](https://github.com/canonical/snapcraft/blob/5317dbebac1c953192ff38e4c6fddd294f979cb1/snapcraft/models/project.py#L628). ### Why it needs to get done Faster iteration for developers - errors should be raised early on when validating the model. This has been reported in https://github.com/canonical/snapcraft/issues/5172