feat: allow optionally installing dependencies via pip (like `gooey`) in `test-on-pr.yml`

[bobleesj]

Problem

Atm, our CI must install everything from conda.txt. But in the case of regolith, it is required to install gooey via pip.

Hence, regolith atm can't use our beautiful reusable script.

Ref: regro/regolith#1258

Proposed solution

Allow optional pip_install section? Please see an example below:

jobs:
  tests-on-pr:
    uses: scikit-package/release-scripts/.github/workflows/_tests-on-pr.yml@v0
    with:
      project: regolith
      c_extension: false
      headless: false
      pip_install: gooey
    secrets:
      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

[sbillinge]

we could do this as the solution. I was wondering whether it would be more widely useful if we let users insert a run: block. I think they could then, in this case, insert a line like pip install -r requirements/pip.txt. But in general it gives them the opportunity to insert any kind of user-defined run.

I am not sure if will be ambiguity about "where" it is inserted and how this will affect success. I would suggest that we keep it simple atm and prescribe where it is inserted and this will "either work or not work" depending on the situation. Later, if people are banging down the door to change the behavior, we can then revisit this choice then.

@bobleesj could you take a look? I think, in general, this would be a good feature because now, as it stands, any tiny customization means that the reusable scripts can't be used and the poor user has to build everything themselves.

[bobleesj]

yeah that sounds good. I will report back here.

[bobleesj]

Implemented in the PR above.