Add flag to optionally limit redirects to url_prefix

[Lukewh]

Done

By default, redirects are very restrictive, this change makes things more open by default, which is fine in 99% of our use-cases.

QA

• You'll need to include this branch in your project.
• Add a couple of redirects to your discourse docs:
  1. /docs/test -> /docs
  2. /docs/test -> https://github.com
• With your Docs initialised with url_prefix="/docs":
  • limit_redirects_to_url_prefix set to True redirect 1. should work and redirect 2. should not.
  • limit_redirects_to_url_prefix unset (or set to False), both redirects should work

Fixes https://warthogs.atlassian.net/browse/WD-2871

[sparkiegeek]

conflicts with main now

[nottrobin]

Don't you want to be including this target in an assert?

[nottrobin]

I have a few wonderings:

• Should a limit on redirect targets perhaps be the default behaviour for all documentation?
• Or, would this be better as a redirect_prefix setting, so you can set the allowed prefix?
• Or should we combine the two, with the default being restrictive but overrideable with a different prefix?

Really the only way to answer this is to do a quick audit of what sorts of redirects currently exist within documentation sets. Do people actually redirect out of the domain, or out of the docs area, in practice?

[anthonydillon]

@Lukewh can you rebase this one please?

[anthonydillon]

Is it same prefix or same origin?

[Lukewh]

Same prefix, e.g. "/docs"

[Lukewh]

I'll fix the tests later - looks like I need to update new ones

[anthonydillon]

@Lukewh is this still valid?