Shorten lifetime of branches

I notice that current devolpment of different issues are merged into `new-cdd-function`. Yet, this branch is 136 commits ahead of our `main` branch. Imho this is bad, as currently `main` cannot used as a base for further development.

So my two suggestions are

1. Figure out when we will merge `new-cdd-function` into `main`, so that future development can actually be based upon `main`.
2. In the future we should limit the lifetime of our branches to prevent this issue from happening again. We could, for example, say that branches (and subsequent pull requests) should be single issue only, but other rules are also possible.

Start by reviewing the history and relationship between `new-cdd-function` and `main`, then read the issue discussion for context on the proposed branch-lifetime problem. Done means the project has an agreed plan for merging the long-lived branch and a documented, accepted rule for future branches and pull requests.

Written by the indexing model from the issue text.