Changes and Information

Please briefly list the changes (main added features, changed items, or corrected bugs) made:

Changed return type from void to bool in check_ and apply_constraints functions of Populations and CompartmentalModel
Added tests for functions in Populations

If need be, add additional information and what the reviewer should look out for in particular:

-

Please check our git workflow. Use the draft feature if the Pull Request is not yet ready to review.

[x] Every addressed issue is linked (use the "Closes #ISSUE" keyword below)
[x] New code adheres to coding guidelines
[x] No large data files have been added (files should in sum not exceed 100 KB, avoid PDFs, Word docs, etc.)
[x] Tests are added for new functionality and a local test run was successful (with and without OpenMP)
[x] Appropriate documentation for new functionality has been added (Doxygen in the code and Markdown files if necessary)
[x] Proper attention to licenses, especially no new third-party software with conflicting license has been added
[ ] (For ABM development) Checked benchmark results and ran and posted a local test above from before and after development to ensure performance is monitored.

[ ] Corresponding issue(s) is/are linked and addressed
[ ] Code is clean of development artifacts (no deactivated or commented code lines, no debugging printouts, etc.)
[ ] Appropriate unit tests have been added, CI passes, code coverage and performance is acceptable (did not decrease)
[ ] No large data files added in the whole history of commits(files should in sum not exceed 100 KB, avoid PDFs, Word docs, etc.)
[ ] On merge, add 2-5 lines with the changes (main added features, changed items, or corrected bugs) to the merge-commit-message. This can be taken from the briefly-list-the-changes above (best case) or the separate commit messages (worst case).

Closes #1061.