allow downstream apps to override docs link

[kecnry]

Description

Similar to #2392, this pull request allows downstream apps which inherit plugins defined in jdaviz to override the "Learn More" link to point to their own docs. If not provided in the plugin class, then the value hardcoded in the .vue file in jdaviz will still apply. This should not affect users of jdaviz in any way.

See spacetelescope/lcviz#43 for how this would be used in lcviz.

Change log entry

• Is a change log needed? If yes, is it added to CHANGES.rst? If you want to avoid merge conflicts,
  list the proposed change log here for review and add to CHANGES.rst before merge. If no, maintainer
  should add a no-changelog-entry-needed label.

Checklist for package maintainer(s)

This checklist is meant to remind the package maintainer(s) who will review this pull request of some common things to look for. This list is not exhaustive.

• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
• Do the proposed changes follow the STScI Style Guides?
• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
• Are docs added/updated as required? If so, do they follow the STScI Style Guides?
• Did the CI pass? If not, are the failures related?
• Is a milestone set? Set this to bugfix milestone if this is a bug fix and needs to be released ASAP; otherwise, set this to the next major release milestone.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[pllim]

Here in Jdaviz, can we just define the URL in the mixin? Then we don't need all the || operations?

[kecnry]

I thought about that, the downside is in order to have access to vdocs/config it would need to be in the init, after calling super (I think), which might be a bit more subtle to remember to do for future plugins that this... but I was on the fence, so if you think that would be cleaner, I can easily switch to that instead.

[pllim]

I see. Maybe this is okay for now then.

[kecnry]

Revisiting this - one advantage to moving the docs link to the plugin class would be that we could programmatically open a new tab from the API... plugin.open_docs(), or similar 🤔 🐱

[pllim]

programmatically open a new tab

Oh, dear. Astronomers have enough tabs open as it is. Do we really want to encourage that even more?

[codecov]

Codecov Report

Patch coverage is 100.00% of modified lines.

Files Changed	Coverage
jdaviz/core/template_mixin.py	100.00%

📢 Thoughts on this report? Let us know!.