Add MS Graph API integration for email notifications in GeoNode

[kishkumar96]

Overview

This pull request integrates Microsoft Graph API as an alternative email backend for GeoNode, replacing or complementing the existing SMTP-based email system. This enhancement improves email security, reliability, and authentication using OAuth2.

Checklist

Reviewing is done by project maintainers, mostly on a volunteer basis. Please help by completing these items where possible.

For all pull requests:

• I have read the contribution guidelines.
• If required, I have sent a Contribution License Agreement (CLA).
• The first PR targets the master branch unless fixing an issue in a specific branch.
• I have verified that my changes are not breaking existing functionalities.

For core and extension modules:

• There is an issue in GeoNode Issues describing this change.
• The issue linked to this PR has appropriate labels and milestones.
• This PR consists of a single commit (or well-organized multiple commits).
• The commit message follows GeoNode’s format: [Fixes #<issue_number>] Title of the Issue.
• The PR title follows GeoNode’s format: [Fixes #<issue_number>] Title of the PR.
• New unit tests have been added to validate this change.
• This PR passes all existing tests (Travis CI will report test results after submission).
• Code formatting passes QA checks:

  black geonode && flake8 geonode

[cla-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have the users @sopac on file. In order for us to review and merge your code, please contact the project maintainers to get yourself added.

[codecov]

Codecov Report

Attention: Patch coverage is 13.33333% with 13 lines in your changes missing coverage. Please review.

Project coverage is 64.11%. Comparing base (d296f7a) to head (343c745).
Report is 12 commits behind head on 4.3.x.

Additional details and impacted files

@@            Coverage Diff             @@
##            4.3.x   #12907      +/-   ##
==========================================
- Coverage   64.14%   64.11%   -0.03%     
==========================================
  Files         872      873       +1     
  Lines       52328    52342      +14     
  Branches     6478     6479       +1     
==========================================
- Hits        33564    33558       -6     
- Misses      17275    17294      +19     
- Partials     1489     1490       +1