[feat] Add OAuth2 support for OpenStreetMap

[mmd-osm]

Fixes #758

Proposed changes

Adding OAuth 2.0 support for OpenStreetMap, since the existing OAuth 1.0a support will be sunset in June 2024.
Multiple applications using python-social-auth won't be able to authenticate anymore at that point.

Types of changes

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• Release (new release request)
• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (PEP8, lint, formatting, renaming, etc)
• Refactoring (no functional changes, no api changes)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Build related changes (build process, tests runner, etc)
• Other (please describe):

Checklist

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• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added documentation to https://github.com/python-social-auth/social-docs

Other information

I've added more details, including a screen recording, in this comment: #758 (comment)

Edits:

• I forced-pushed the branch to include the DEFAULT_SCOPE parameter.
• Another rebase due to "[pre-commit.ci] auto fixes from pre-commit.com hooks " being merged into master.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (22dcdaa) 77.70% compared to head (85da2df) 77.77%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #877      +/-   ##
==========================================
+ Coverage   77.70%   77.77%   +0.06%     
==========================================
  Files         345      347       +2     
  Lines       10574    10604      +30     
  Branches      699      699              
==========================================
+ Hits         8217     8247      +30     
  Misses       2200     2200              
  Partials      157      157              

Flag	Coverage Δ
unittests	77.77% <100.00%> (+0.06%)	⬆️

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[nijel]

Merged, thanks for your contribution!