T2R does not handle ENV[RAILS_RELATIVE_URL_ROOT]

[tonischilling]

Bug summary
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To Reproduce
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2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
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Device information

• Type: [e.g. Desktop / Laptop / Handheld]
• OS: [e.g. Windows 10 / Ubuntu 18.4 / MacOS 10.14.4]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context
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[tonischilling]

Hrrg! it happened again ...
so Description comes here

Bug summary
When using Redmine through a Reverse-Proxy with an URL-prefix,
this prefix will not be reproduced in T2R's "backward links".

To Reproduce

1. Host your Redmine through a reverse proxy with an URL-prefix
   e.g. "https://from.outside.de/redmine/..." => goes internally to "http://12.34.56.78:8080/redmine/..."
2. Use it from outside
3. (most of?) T2R´s backward links will not contain the URL-Prefix - and thus they are broken.

Expected behavior

• e.g.: "https//from.outside.de/time_entries.json?user_id=me&limit ..."
  should be "https//from.outside.de/**redmine/**time_entries.json?user_id=me&limit ..."

Context

• T2R-4.3.1, Redmine-4.2.2, Rails-5.2.6, Ruby-2.7.4,
• Apache-Config contains
  SetEnv RAILS_RELATIVE_URL_ROOT /redmine
  which is available in Rails as ENV[RAILS_RELATIVE_URL_ROOT]
  and correctly applied the other Redmine-Backward-Links

[tonischilling]

Could fix it -- for me:
(
see relevant parts of "git diff v4.3.1 all-my-hacks | tee relative_url.vimdiff"
Do not trust the line numbers, because I hacked a couple of other things, which are not part of the diff
relativ_url.vimdiff.txt
)
Probably there´s is a better - more RAILS-ish way - to do that, but for now and for me it works.

[jigarius]

I've been very busy lately. I'll try to get this one done next. Thanks for the detailed report.