PHQ-8 task.

[RudolfCardinal]

Built from "rich_argparse_help" branch.

Checklist for new tasks:

• [X] Add task to relevant menus
• [X] Generate code documentation
• [X] Update docs/source/changelog.rst
• [X] Test documentation rebuilds without errors
• [ ] If the text of the task cannot be submitted here for copyright reasons, there is a template XML file under server/camcops_server/extra_string_templates.

Please [X] all the boxes above that apply

[martinburchell]

Looks good.

I just compared PHQ8 with PHQ9 to see the differences. I note that you've "forked" PHQ9, leaving two separately maintained tasks rather than try to set up any kind of relationship between the two through e.g. inheritance. That seems OK to me.

[RudolfCardinal]

Thanks. Yes -- could do it either way but split primarily for code legibility.