feat: Feat/service accounts

[St4NNi]

This PR builds on top of PR #90 . It adds the long awaited ServiceAccount feature.

Service accounts are similar to regular users but have some restrictions:

• Service accounts are always bound to exactly one project and cannot be added to other projects
• SAs are managed via a separate API that has a similar interface as the user equivalent but can be called as Project::ADMIN
• Service accounts can do the same things as regular users with the exception user management requests, these are (for now) "real" user only.

This PR implements all necessary API and DB requests that make it possible to create, update and manage service accounts by Project Admins. The API should be treated as BETA for now.

The PR also adds some optimizations in the ApiToken <-> gRPC Token handling by introducing a TryFrom implementation, this allows us to remove some token conversion boilerplate from crud/user.rs

Fixes: #38

[codecov]

Codecov Report

Patch coverage: 12.50% and project coverage change: -2.02 ⚠️

Comparison is base (dd56ae6) 54.19% compared to head (077edbe) 52.18%.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev      #91      +/-   ##
==========================================
- Coverage   54.19%   52.18%   -2.02%     
==========================================
  Files          48       49       +1     
  Lines       10566    10950     +384     
==========================================
- Hits         5726     5714      -12     
- Misses       4840     5236     +396     

Impacted Files	Coverage Δ
src/database/crud/object.rs	55.74% <ø> (ø)
src/database/crud/service_accounts.rs	0.00% <0.00%> (ø)
src/error.rs	24.53% <0.00%> (ø)
src/server/services/internal_proxy_notifier.rs	0.00% <ø> (ø)
src/server/services/object.rs	44.16% <ø> (ø)
src/server/services/service_account.rs	0.00% <0.00%> (ø)
src/server/services/user.rs	36.47% <ø> (ø)
src/server/services/authz.rs	54.30% <8.33%> (-1.38%)	⬇️
src/database/crud/authz.rs	76.21% <17.85%> (-11.01%)	⬇️
src/server/services/internal_authorize.rs	27.08% <33.33%> (ø)
... and 5 more

... and 1 file with indirect coverage changes

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[das-Abroxas]

For me, it seems that the most important things have been taken into account, that service accounts cannot be abused. However, there is now a possibility for users that services can work with the AOS independently of personal accounts ✔️