feat: data connectors in project creation

[olevski]

Initial implementation for creating data connectors that can be owned by projects.

/deploy

[olevski]

This change is part of the following stack:

• feat: authz schema changes for data connectors #615
  • feat: data connectors in project creation #617 ◀
    • feat: adapt namespace endpoints #638
      • feat: reading DC links requires read on the DCs #642

_{Change managed by git-spice.}

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-ds-617.dev.renku.ch