Adds checking for downgrade redirects, storing of redirect domain and howing redirect domain in direct tests

[WKobes]

Fixes #270
Fixes #1521

This PR basically adds three functionalies:

• storing of redirection domain (in case of Location header) on webtests
• checking if the redirection to this other domain is done over HTTPS (no downgrade redirect), as discussed in HTTPS redirect test does not fail when redirecting from HTTPS to HTTP on other domain #1521
• showing the stored redirection domain in the direct tests on the report view, if the domain is testable at page load, solving Display redirect domain as 'directly test' option - website test #270

I decided to store the redirection domain in the report since this way the report result remains static and allows us to represent the invalid redirect in the report. Old report pages will show the redirection domain in the direct tests view for as long as this domain is testable.

Todo's

• Add new content strings
• Change test explanation (since we now do check the next outgoing redirect)
• Add Django migrations (could not get the migration from docker)
• fix Details on HTTPS redirect subtest failure reason in tech table #1428

Questions/to check:

• Does storing redirect domain have any implications for e.g. privacy?
• Passing stored redirect domain as in interface/views/domain.py#L120 feels a bit fishy, can it be done better?
• Possible a broken HTTP server sending multiple Location headers could break stuff
• Currently does not check if response code is 30x, should we do this?
• Will using a formatted string like checks/categories.py#L946 work in translation files?

[bwbroersma]

• [WIP] Fix #1314 - security.txt full url in finding #1319 (comment) applies here as well, also needs to be added to the API, and update openapi.yaml and bump the API version.
• Maybe also look into Details on HTTPS redirect subtest failure reason in tech table #1428