[server] Optimize getTeamMembers (N queries → 1 query)

[jankeromnes]

Fixes #4470

I've also added a test (passed! ✅) and getting team member infos still works fine:

[jankeromnes]

@geropl On a side note, while manipulating identities in TeamDBSpec, I stumbled on a weird failure in UserDBSpec:

  1) UserDBSpec
       createUserAndFindById:

      AssertionError: expected { Object (id, creationDate, ...) } to have deep property 'identities' of [ Array(1) ], but got [ Array(1) ]
      + expected - actual

           "authId": "1234"
           "authName": "gero"
           "authProviderId": "GitHub"
           "deleted": false
      -    "primaryEmail": "tom@example.com"
      +    "primaryEmail": [undefined]
           "readonly": false
           "tokens": []
         }
       ]

See: https://werft.gitpod-dev.com/job/gitpod-build-jx-optimize-get-team-members.2

That's when I realized that identities are not deleted when users are deleted:

gitpod/components/gitpod-db/src/typeorm/entity/db-user.ts

Lines 41 to 49 in a6c5481

	@OneToMany(type => DBIdentity,
	identity => identity.user,
	{
	eager: true,
	cascadeInsert: true,
	cascadeUpdate: true
	// , cascadeRemove: true // In the docs but not the code???
	}
	)

My drive-by fix here was to also clean up the DBIdentity repo after cleaning up DBUser (in both UserDBSpec and TeamDBSpec). But that pre-existing comment makes a good point -- maybe we should cascadeRemove identities?

[AlexTugarev]

Wasn't the reason that we are not cascade deleting related items that it needs to go through dbsync? i.e. we need to enable soft-deletion for that.

[csweichel]

/werft run

👍 started the job as gitpod-build-jx-optimize-get-team-members.5

[jankeromnes]

Anyone please approve. Can be safely merged any time.

[csweichel]

LGTM

[jankeromnes]

Thanks!

This was already merged as 236d81d (as part of #4490).