Provide proactive feedback when trying to change team type to incompatible type

[knolleary]

Closes #4377

This provides better feedback if a team upgrade is blocked due to the current usage exceeding any limits on the target team.

My first iteration was to add the check on the backend for the path where a team is setting up billing - it was already handled for the case of changing type when billing is already setup. This ensures any issue is reported before they are sent to stripe.

However, the feedback isn't great - and would be better to be more proactive in the UI. So the second iteration (3rd commit) copies the limit checks into the front end and lets us show a more helpful message to the user:

The specific errors shows above are based on how I happen to have my Starter team type setup locally; so don't get distracted by the specific numbers.

Also need to highlight the checks are based purely on Members/Device/Instance count limits. It doesn't check if they are using features (eg Team Library) that are unavailable at the target tier. We don't maintain flags on feature usage within a team, so that's out of scope (and not proposing it comes into scope any time soon).

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There is currently limit test coverage for this. We're missing base coverage in a couple different areas here for the existing code.

I have added basic verification the UX blocks changing to a team that is not compatible with current usage - but it isn't exhaustive.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.

Project coverage is 78.12%. Comparing base (ccd5b75) to head (7004aaf).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
forge/ee/routes/billing/index.js	0.00%	13 Missing ⚠️
forge/db/models/Team.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4378      +/-   ##
==========================================
- Coverage   78.17%   78.12%   -0.06%     
==========================================
  Files         295      295              
  Lines       13985    13994       +9     
  Branches     3159     3163       +4     
==========================================
  Hits        10933    10933              
- Misses       3052     3061       +9     

Flag	Coverage Δ
backend	78.12% <0.00%> (-0.06%)	⬇️

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[knolleary]

Have added basic coverage to verify the UI blocks changing to a 'lower' type.

[Steve-Mcl]

Happy with the code.

Do we have a team on prod that we can verify this after it is deployed?

[hardillb]

@Steve-Mcl do we want to merge this and then I can test it?

[Steve-Mcl]

@hardillb - yes, fine by me Ben

[hardillb]

Verified on Staging where I had a Teams, team with more users and instances than allowed in starter.