Force html processing for all formats except html, js and json

[danidoni]

The default html format makes the Cancel button to be processed wrongly as html
instead of js.

This change allows the Cancel button to work as ajax, as well as the rendering
of package pages for packages with dots in its name like
"yaml-cpp.openSUSE_Leap_15.2_Update".

Fixes #10510

---

If this PR requires any particular action or consideration before deployment,
please check the reasons or add your own to the list:

• Requires a database migration that can cause downtime. Postpone deployment until maintenance window[1].
• Contains a data migration that can cause temporary inconsistency, so should be run at a specific point of time.
• Changes some configuration files (e.g. options.yml), so the changes have to be applied manually in the reference server.
• A new Feature Toggle[2] should be enabled in the reference server.
• Proper documentation or announcement has to be published upfront since the introduced changes can confuse the users.

[1] https://github.com/openSUSE/open-build-service/wiki/Deployment-of-build.opensuse.org#when-there-are-migrations
[2] https://github.com/openSUSE/open-build-service/wiki/Feature-Toggles-%28Flipper%29#you-want-real-people-to-test-your-feature

[dmarcoux]

I would be interested to know why is this needed for a package, but not for a project. Why?

[danidoni]

I would be interested to know why is this needed for a package, but not for a project. Why?

Because we're forcing a specific format for packages but not for projects.

So a project can choose whatever format it needs for the response, but a package is forced to be treated as an :html no matter what.

[obs-bot]

Review app will appear here: http://obs-reviewlab.opensuse.org/danidoni-fix-cancel-button

[danidoni]

I've opted for closing this PR in favor of #10879, because the new changes imply moving the Edit link close to the edited fields.