Added manager to the admin dashboard

[BenjaminCharmes]

Closes #1348

[codecov]

Codecov Report

❌ Patch coverage is 71.69811% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.02%. Comparing base (b121182) to head (af47bb4).

Files with missing lines	Patch %	Lines
pydatalab/src/pydatalab/routes/v0_1/admin.py	71.69%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1352      +/-   ##
==========================================
- Coverage   80.10%   80.02%   -0.08%     
==========================================
  Files          70       70              
  Lines        4755     4807      +52     
==========================================
+ Hits         3809     3847      +38     
- Misses        946      960      +14     

Files with missing lines	Coverage Δ
pydatalab/src/pydatalab/routes/v0_1/admin.py	70.45% <71.69%> (+3.78%)	⬆️

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[cypress]

datalab    Run #3919

Run Properties:   Passed #3919  •  7d33fc31ca ℹ️: Merge af47bb4486001f23f724699e7dc3d956cc0888b9 into b121182e7a2c4ca1eebd268ed0b8...

Project	datalab
Branch Review	bc/admin-manager
Run status	Passed #3919
Run duration	07m 41s
Commit	7d33fc31ca ℹ️: Merge af47bb4486001f23f724699e7dc3d956cc0888b9 into b121182e7a2c4ca1eebd268ed0b8...
Committer	Ben Charmes
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	336
View all changes introduced in this branch ↗︎

[ml-evs]

Thanks for this @BenjaminCharmes, just tried it out, whilst it works quite nicely in usual cases, I seemed to be able to crash it by making user A manager of another user B, and then making that user B manager of user A, where I get "cyclic object value" as an error.

This seems to happen at arbitrary depths too, i.e., A -> B -> C -> A manager loops.

Finally, it would be good to add some tests for this new API route, i.e., make a user another user's manager, check that they have to be a manager/admin themselves, and make sure they can see that user's items once they are their manager.