add anonymous login

[houfu]

What kind of change does this PR introduce?

Fixes #504.
Follows https://github.com/supabase/auth-js/blob/f131300d753634fcf3fbc93dc7a762031f096749/src/GoTrueClient.ts#L370-401
With new types as well

Feedback welcomed.

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[silentworks]

I knew I should have checked PRs before spending my day doing one. I just worked on this yesterday to now see your PR. I will get this reviewed and merged in soon.

[houfu]

Sorry about that 🙏

[codecov]

Codecov Report

Attention: Patch coverage is 24.13793% with 22 lines in your changes missing coverage. Please review.

Project coverage is 44.10%. Comparing base (4a18e21) to head (ad2179b).
Report is 10 commits behind head on main.

Files	Patch %	Lines
supabase_auth/_async/gotrue_client.py	8.33%	11 Missing ⚠️
supabase_auth/_sync/gotrue_client.py	8.33%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #528      +/-   ##
==========================================
- Coverage   44.38%   44.10%   -0.29%     
==========================================
  Files          23       23              
  Lines        2032     2061      +29     
==========================================
+ Hits          902      909       +7     
- Misses       1130     1152      +22     

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[silentworks]

I'm going to roll my changes into yours as I can see you've made changes to the sync client but not the async one

Sorry about that 🙏

No, actually thank you for this. It's good to see more first time contributors contributing to this project. I really appreciate this PR.