Formalize process to integrate apps

[chazapis]

Currently, integrations with JupyterHub, Argo, Harbor, Grafana, and OpenBio are hard-coded. We need a well-defined process to add an application to Karvdash, which will allow decoupling the integration from the codebase and easily adding new apps.

Each app should define:

• Name, icon, and URL for placing in the menu.
• Secret containing OIDC info for the app (to be used by the OAuth 2.0/OIDC provider).
• Hooks (probably jobs) to run when creating the app or the user logs in.

These could be included in a CRD.