feat: add support for presharedkey auth in the Playground

[jon-whit]

Description

This wires up auth support in the Playground for OpenFGA servers setup with preshared key authentication.

References

#133

Review Checklist

• I have added documentation for new/changed functionality in this PR or in openfga.dev
• The correct base branch is being used, if not main

[jon-whit]

@rhamzeh @matldupont looks like the preshared auth support in the embedded Playground works mostly (see attached video). The only hiccup is that fetching the predefined model from the default Playground store fails because the local auth key isn't appropriate for the hosted Playground.

Do you guys have some recommendations on how we should resolve that elegantly?

auth-playground.mov

[rhamzeh]

The only hiccup is that fetching the predefined model from the default Playground store fails because the local auth key isn't appropriate for the hosted Playground.

Is that what's happening? Let's discuss this in an issue in that repo, because the local playground should not be talking to the hosted version.

[rhamzeh]

Error not related, should be fixed in Play/SDK repo

[codecov-commenter]

Codecov Report

Merging #141 (f1232a5) into main (b4c45a4) will decrease coverage by 0.11%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
- Coverage   75.68%   75.57%   -0.12%     
==========================================
  Files          77       77              
  Lines        8494     8504      +10     
==========================================
- Hits         6429     6427       -2     
- Misses       1680     1691      +11     
- Partials      385      386       +1     

Impacted Files	Coverage Δ
pkg/cmd/run.go	0.00% <0.00%> (ø)
server/commands/check.go	86.27% <0.00%> (-0.57%)	⬇️

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