deduplicate USER_AGENT specification in Dockerfile

[breunigs]

Testing:

docker build ./4.3/ -t some:name && \
  docker run --entrypoint /bin/bash some:name \
  -c 'echo user agent is: $USER_AGENT'

cc @leonardehrenfried who initially introduced the comment

I couldn't find a policy/developer guide if all or only the most recent version should be patched. I can add the older ones if desired.

[what-the-diff[bot]]

PR Summary

• Introduced Dynamic Arguments This PR modifies the Dockerfile associated with version 4.3 of the project to make it more adaptable. The key changes include the addition of NOMINATIM_VERSION and USER_AGENT as arguments. This will help in managing versions and user-agents more flexibly.

• Elimination of Redundancy It also efficiently removes the repetitive definition of these variables from different lines of the codes. This reduces clutter making the Dockerfile more readable.

• Enhanced Consistency Furthermore, the PR consistently replaces the existing values of NOMINATIM_VERSION and USER_AGENT with these arguments in many places. This will ensure system-wide uniformity and reduce errors.

This change overall assists in simplifying the configuration process and enables more effective management of versions and user agents in the project.

[philipkozeny]

Thanks for the PR.

@all-contributors please add @breunigs for code

[allcontributors[bot]]

@philipkozeny

I couldn't determine any contributions to add, did you specify any contributions? Please make sure to use valid contribution names.

I've put up a pull request to add @breunigs! :tada: