Bug 1259173 - Adjust Akismet payload

[jwhitlock]

Rewrite the RevisionForm tests to setup forms for validation in the same way the views set them up (create, edit, and translate). Then:

Update the Akismet payload:

• Add HTTP headers
• Add blog parameter (front page of site), and fix default if omitted
• Add permalink parameter (page that is being edited
• Minimize comment_content to the changed and new content

Further improvements:

• Move payload generation to new AkismetRevisionData class, so the same logic can be used in the RevisionForm as other places
• Save Akismet data in RevisionIP instance, and replay for submit-ham and submit-spam.
• Add read-only displays of Akismet data to admin detail views.

This PR should be manually merged:

• The first commit rewrites the tests, and the PR will be easier to understand after merging (optional)
• The second-to-last commit includes a database migration that should be applied in production before the last commit
• The last commit adds the code that uses the new database column.

[jezdez]

admin instances are global, that will lead to threading issues

[jwhitlock]

AdminFormWithRequest makes more sense now. Is that the pattern to use here as well, or do you have a better solution?

Update - AdminFormWithRequest won't help here. Investigating InlineModelAdmin.

Update 2 - Nope, InlineModelAdmin is for editing to-many relations. Maybe a custom template?

[jwhitlock]

Force push to change the strategy for displaying captured data from RevisionIP when creating a RevisionAkismetSubmission from the revision dashboard. Previously, the request query parameter was captured in get_fields, which was not thread safe. Now, add_view and change_view are adjusted to inject the data into the template context, and the template displays it (almost) like it was a field.

[jwhitlock]

Force push to rebase and renumber the migration.