Document re-evaluation of routing rules on signal updates

[tcoenen]

Description

A part of the discussions around PR#1120 was the need to document the behavior of Routing expressions on updates to the underlying nuisance complaint (Dutch: melding). This PR adds that documentation.

Checklist

• Keep the PR, and the amount of commits to a minimum
• The commit messages are meaningful and descriptive
• Check that the branch is based on main and is up to date with main
• Check that the PR targets main
• There are no merge conflicts and no conflicting Django migrations

[tcoenen]

@bartjkdp What is the name of the feature flag?

[bartjkdp]

@tcoenen if you want, you can propose the name of the feature flag. I will implement it accordingly in #1120.

[tcoenen]

@bartjkdp I don't have a particular name in mind. You could use DSL_RUN_ROUTING_EXPRESSIONS_ON_UPDATES if you have no better name for it yourself.

[bartjkdp]

@tcoenen I like this name, I will use it in my PR as well.

[tcoenen]

I updated the document with the correct feature flag name. I think this document is now complete and I will change the PR status to ready for review.

[vanbuiten]

Can you add these changes to PR #1120 instead of main. That way we can merge the whole functionality as one. OR we should merge #1120 and after that #1122.

[vanbuiten]

Approved