Add uploaded_blob context manager, allow calling of model clean() with overridden settings

[thclark]

Contents (#84)

New features

• Add uploaded_blob context manager, useful for unit testing

Fixes

• Allow field cleaning to happen inside an overridden context
• Correct implementation of headers for limiting content length range
• Make upload_blob woth with default destination path helper

Operations

• Remove deprecated setting from devcontainer json

Refactoring

• Remove redundant context in test

Testing

• Test uploaded_blob context manager

[codecov]

Codecov Report

Attention: Patch coverage is 93.61702% with 3 lines in your changes missing coverage. Please review.

Project coverage is 68.86%. Comparing base (50ffc67) to head (576c27b).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
django_gcp/storage/fields.py	91.17%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
+ Coverage   68.28%   68.86%   +0.57%     
==========================================
  Files          43       43              
  Lines        1996     2004       +8     
==========================================
+ Hits         1363     1380      +17     
+ Misses        633      624       -9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.