Bump websockets from 7.0 to 9.1 in /src/server

[dependabot]

Bumps websockets from 7.0 to 9.1.

Changelog

Sourced from websockets's changelog.

9.1 ...

May 27, 2021

.. note::

**Version 9.1 fixes a security issue introduced in version 8.0.**
Version 8.0 was vulnerable to timing attacks on HTTP Basic Auth passwords.

9.0.2 .....

May 15, 2021

• Restored compatibility of python -m websockets with Python < 3.9.

• Restored compatibility with mypy.

9.0.1 .....

May 2, 2021

• Fixed issues with the packaging of the 9.0 release.

9.0 ...

May 1, 2021

.. note::

**Version 9.0 moves or deprecates several APIs.**
Aliases provide backwards compatibility for all previously public APIs.


:class:~datastructures.Headers and
:exc:~datastructures.MultipleValuesError were moved from
websockets.http to :mod:websockets.datastructures. If you're using
them, you should adjust the import path.


The client, server, protocol, and auth modules were
moved from the websockets package to websockets.legacy
sub-package, as part of an upcoming refactoring. Despite the name,
they're still fully supported. The refactoring should be a transparent
upgrade for most uses when it's available. The legacy implementation
will be preserved according to the backwards-compatibility policy_.

... (truncated)

Commits

• d0f3288 Bump version number.
• 547a26b Use constant-time comparison for passwords.
• a14226a Bump version number.
• 8900c13 Add mypy to dictionary.
• 0713dbf Add test coverage.
• b99c4fe Restore real imports for compatibility with mypy.
• e44e085 Use relative imports everywhere, for consistency.
• 70fadbf Restore compatibility with Python < 3.9.
• 217ac2d Fix broken link.
• fc176f4 Bump version number.
• Additional commits viewable in compare view

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