chore: Release 8.0.0

[TheRealAgentK]

Summary

Prepares Raygun4Py 8.0.0 and modernizes contributor/CI dependency management without pinning the public runtime dependency contract.

Breaking change

• Drop Python 3.9 support; Raygun4Py now requires Python 3.10+

Dependency and CI hardening

• Add authoritative PEP 735 development dependency groups while retaining the existing dev extra as a compatibility interface
• Exercise the legacy .[dev] install in the Python 3.10 CI job and dependency groups in Python 3.11–3.14
• Add a pip 26.1.2-generated PEP 751 lock snapshot for CPython 3.13 on Linux x86-64
• Keep the Python 3.10–3.14 matrix on unlocked resolution and add one hash-verified locked CI lane
• Lock the editable/build toolchain, disable hidden build isolation in the locked lane, and run pip check
• Add mypy and package-build validation
• Document normal, legacy, locked, regeneration, functional-test, and release workflows

Compatibility fixes

• Preserve Raygun4Py's existing jsonpickle string-key payload wire format while isolating jsonpickle 4.1.2's transitional warning
• Use Flask's supported package metadata API instead of its deprecated __version__ attribute
• Preserve Flask error-report robustness by falling back when distribution metadata is unavailable, rather than masking the original exception

The lockfile is contributor/CI-only. It is not shipped as Raygun4Py's public installation contract, and downstream applications should continue managing their own locks.

Validation

• Ruff format and lint: passed
• Mypy: passed
• Unit and middleware suite with deprecations treated as errors: 80 passed, 23 functional tests skipped without credentials
• Live functional suite against a test Raygun application: 23 passed
• Legacy-extra, dependency-group, and locked fresh installs: passed
• pip check: passed
• Lock regeneration: byte-for-byte reproducible
• sdist and wheel build: passed
• twine check: passed for both artifacts

Release status

Raygun4Py 8.0.0 has been published to PyPI from the checked artifacts; both published SHA-256 hashes match the locally validated files. The changelog is finalized with the 23/07/26 release date. The remaining steps are to squash-merge this PR and create the v8.0.0 GitHub release.