fixes 2743

[WolfgangFahl]

Fixes #2743

Description

add /backend route and template

Caveats

Please list anything which has been left out of this PR or which should be considered before this PR is accepted
Check any of the following which apply:

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
  • I have made corresponding changes to the documentation
• This change requires new dependencies (please list)

If you make changes to the Python code

• My code passes the tox check, I can receive warnings about tests, documentation or both

Testing

https://scholia.wikidata.dbis.rwth-aachen.de/backend

Checklist

• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have not used code from external sources without attribution
• I have considered accessibility in my implementation
• There are no remaining debug statements (print, console.log, ...)

[egonw]

Can you please have a look at the code analysis messages?

[WolfgangFahl]

Done and improved

[egonw]

@WolfgangFahl, I note you accidentally sneaked in the port config feature from another PR: ad-freiburg@c6f32f5

And for the other two config parameters, I wrote this patch: ad-freiburg@e47078c

And this patch to fix the flake errors: ad-freiburg@0dff464

[egonw]

See most recent comment.