Add model policies view

[steverydz]

Done

Built the policies view

How to QA

• Go to https://snapcraft-io-4346.demos.haus/login-beta and login
• Go to https://snapcraft-io-4346.demos.haus/admin/njwQYXFnS7ppo7LaGxoh7aqVZc1CPi26/models/test_model_without_api_key/policies
• Check that there are policies in the table
• Check that the signing key links to the signing key page (this will be blank)
• Check that you can create a policy

Issue / Card

Fixes https://warthogs.atlassian.net/browse/WD-4738
Fixes https://warthogs.atlassian.net/browse/WD-4740

[webteam-app]

Demo starting at https://snapcraft-io-4346.demos.haus

[codecov]

Codecov Report

Merging #4346 (9701c86) into main (7682768) will not change coverage.
The diff coverage is n/a.

❗ Current head 9701c86 differs from pull request most recent head ea8865b. Consider uploading reports for the commit ea8865b to get more accurate results

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  Lines        6814     6814           
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  Misses        964      964           

Flag	Coverage Δ
python	85.85% <ø> (ø)

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[Lukewh]

If you go to a different model and policy list, the old policy information is still there:

Maybe clear the data on the equivalent of an "unmount"?

[Lukewh]

👍 LGTM