Upgrade Strategy to MyMLH v4 API

[jonmarkgo]

Update to MyMLH API v4

This PR updates the omniauth-mlh gem to use the MyMLH API v4 endpoints and introduces several breaking changes that warrant a version bump to 2.0.0.

Changes

• Update API endpoints to use v4 (new base URL: https://api.mlh.com)
• Add new granular scope system with default scopes
• Remove support for Implicit Grant flow
• Update documentation with breaking changes
• Add migration guide for v2.0.0
• Update examples with new scope format
• Enhanced test suite with improved data structure handling

Breaking Changes

1. New API Endpoints

   • The API now uses https://api.mlh.com as the base URL
   • User data is now fetched from /v4/users/me

2. Updated Scope System

   • New granular scope system
   • Default scopes: public user:read:profile user:read:email
   • The old scope system (e.g., 'default email birthday') is no longer supported

3. Authentication Flow

   • Only Authorization Code Flow is supported
   • Implicit Grant Flow has been removed

Test Suite Improvements

1. Added activesupport as a development dependency to support deep_symbolize_keys functionality
2. Updated test data structure to better match v4 API response format, including nested objects for:
   • School information
   • Company details
   • User profile data
3. Fixed hash key transformation in tests to properly handle nested data structures
4. Enhanced test coverage with more comprehensive API response data

Testing

• Updated test suite to reflect new API endpoints and response format
• Verified OAuth flow with new scopes
• Confirmed backward incompatibility is properly documented
• All 16 test cases passing with 97.83% line coverage

Link to Devin runs:

• https://preview.devin.ai/devin/92bef702cbe0482d9a674c2ab60d666a
• https://preview.devin.ai/sessions/ae3199dcfa6144a088bf73df81941e48
• https://preview.devin.ai/sessions/c38d66973fe14b3f848311db35f9625d

[jonmarkgo]

Working MyMLH v3 example: https://gist.github.com/jonmarkgo/1881ab9da877de26c4b1a267350690d8/revisions#diff-f965f92b425fb2f75d38b491b2625fe21b8af20b7666217546bce8a42b198ea4

Working MyMLH v4 example: https://gist.github.com/jonmarkgo/1881ab9da877de26c4b1a267350690d8/revisions#diff-9ad32be17347f0cdcc9a38ac9af49d418554f067f3aac5885cf9bddfcee0556f

Note that for the v4 example, I have a tmp branch of this PR that changes the URL to beta.my.mlh.io rather than my.mlh.io