add draft OpenFGA client

[leovalais]

Important

Not to be merged into dev directly

Note

This is a lengthy PR which also requires some amount of OpenFGA knowledge to be understood. It's probably better to peer review it.

Draft OpenFGA client.

• Will be moved into editoast's workspace when ready (it's currently outside for dev comfort)
• Only a few operations have been implemented
• Meant to remain a new sub-crate which will be included in editoast_authz (in which we'll map the authorization model, define our objects, their conversion, relations, etc.)
• The fga binary is necessary to run unit tests for now: https://github.com/openfga/cli

TODO:

• Implement all the operations we'll need
  • Operations needed for the roles reimplementation
  • POST /stores/{}/list-users
  • POST /stores/{}/stream-list-objects
  • POST /stores/{}/expand
  • POST /stores/{}/read
  • POST /stores/{}/batch-check
  • Other operations currently not needed, but since there's so few of them, we may want to implement them for completeness?
• Keep an authorization_model_id in the client to forward it to requests—as advised by OpenFGA
• Improve tests utils
• Documentation (for real this time 👀)
  • mod client
  • mod model
• INSTRUMENT EVERYTHING
• Setup OpenFGA in docker compose

About macros

Important

Expecting feedback on this point

This crates introduces a few macro_rules, which are only used for tests currently.

• relations! allows defining typed relations concisely to allow quick comparisons with the OpenFGA schema. I think we should keep this one, that'll help the review process and reduce straightforward boilerplate.
• fga_type! declares the newtype structs representing the types of OpenFGA and generates a few implementations. I think this one should remain a #[cfg(test)] definition. However I think derive macros derive(fga::User, fga::Object) would help us and cost nothing as they are trivial to implement.
• fga! allows manipulating and instantiating types and relations with the same syntax as OpenFGA, but in a type-safe way. This is particularly useful for the conciseness of unit tests. I think it should be exported.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 0% with 255 lines in your changes missing coverage. Please review.

Project coverage is 81.41%. Comparing base (fd288d3) to head (ac0adfd).

Files with missing lines	Patch %	Lines
fga/src/client.rs	0.00%	255 Missing ⚠️

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Additional details and impacted files

@@                      Coverage Diff                      @@
##           lva/roles-openfga-edition   #10504      +/-   ##
=============================================================
- Coverage                      81.80%   81.41%   -0.39%     
=============================================================
  Files                           1073     1074       +1     
  Lines                         106716   107105     +389     
  Branches                         730      730              
=============================================================
- Hits                           87300    87201      -99     
- Misses                         19377    19865     +488     
  Partials                          39       39              

Flag	Coverage Δ
editoast	74.25% <ø> (-0.03%)	⬇️
front	89.34% <ø> (ø)
gateway	2.18% <ø> (ø)
osrdyne	2.98% <0.00%> (-0.31%)	⬇️
railjson_generator	87.50% <ø> (ø)
tests	87.05% <ø> (ø)

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