[Multi-Tenant] `auth` tenants table

[njlie]

The authorization server will need to maintain its own tenants table, so that it may present clients with the correct identity server during interactions.

The auth tenants table should implement the following schema:

tenants {
  id: string
  idpConsentUrl: string (URL)
  idpSecret: string
}

Note that the id is not generated by the auth database, but is instead provided during the creation process and should correspond directly to the id of a tenant on the backend.

• [ ] Create auth tenant table migration
• [ ] Create model.ts file for tenant model