WIP: Implement Issue forms

[Wazzaps]

Implements #20232.

There's no dev-facing API for this feature, it's pretty much all GUI.

This is my first time writing Go beyond 10 lines of code, look for beginner mistakes :)

Screenshots:

Click to expand

#### Choose template 

Form

Result

Features:

• Parsing most of Github's syntax for issue forms
• Form-style templates show up in template selector
• Template rendering
• Backend that converts the form fields to Markdown (with no clientside js!)
• Display template validation errors in template chooser
• Optionally place certain fields in yaml frontmatter instead
• File upload
• A good design
• Multi-select dropdowns -> replaced with checkboxes in the meantime
• "Required" tag for most field types
• Auto-Assign people based on template -> Need to be done for md templates as well, out of scope
• PR form templates -> out of scope for this PR
• Graphical issue builder -> later
• Template linting when editing online
• A way to extract the form fields reliably / programmatically (maybe a webhook during submit?)
• Form localization
• Don't include empty fields? (deviates from GH behaviour)
• Additional (gitea) features
• config.yml
  • Contact links
    • Warn when leaving site?
  • blank_issues_enabled: false

Known issues:

• Tabindex is broken (cannot tab between fields) Fixed
  • Seems like you can't tab out of a markdown editor, affects normal issues too, out of scope
• Clicking submit while required fields aren't set breaks the submit button
• Pasting images doesn't upload them in form (because no file upload widget in page)

[Wazzaps]

Hmm, I cannot reproduce the "Imports are sorted wrong" lint error on my side, and I can't find a tool that reorders differently them from what they are currently.
Could you take a look? @lunny

[codecov-commenter]

Codecov Report

Merging #20778 (76ad295) into main (3d7058a) will decrease coverage by 0.00%.
The diff coverage is 15.75%.

@@            Coverage Diff             @@
##             main   #20778      +/-   ##
==========================================
- Coverage   47.01%   47.00%   -0.01%     
==========================================
  Files         982      983       +1     
  Lines      136101   136231     +130     
==========================================
+ Hits        63989    64040      +51     
- Misses      64250    64331      +81     
+ Partials     7862     7860       -2     

Impacted Files	Coverage Δ
modules/context/repo.go	49.17% <0.00%> (-2.63%)	⬇️
modules/structs/issue_form.go	0.00% <0.00%> (ø)
routers/web/repo/issue.go	36.38% <23.21%> (-0.36%)	⬇️
routers/web/user/setting/account.go	17.82% <0.00%> (-7.83%)	⬇️
modules/process/manager_exec.go	86.04% <0.00%> (-6.98%)	⬇️
modules/queue/queue_channel.go	79.62% <0.00%> (-0.93%)	⬇️
services/pull/pull.go	40.18% <0.00%> (-0.16%)	⬇️
routers/api/v1/repo/pull.go	47.17% <0.00%> (+0.17%)	⬆️
models/issues/comment.go	50.32% <0.00%> (+0.54%)	⬆️
models/notification.go	63.32% <0.00%> (+1.09%)	⬆️
... and 8 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[lunny]

Hmm, I cannot reproduce the "Imports are sorted wrong" lint error on my side, and I can't find a tool that reorders differently them from what they are currently. Could you take a look? @lunny

Thanks @zeripath did that.

[Wazzaps]

Added indication if templates don't pass validation, with an error string.
Need to localize this.

[lunny]

Added indication if templates don't pass validation, with an error string. Need to localize this.

Shouldn't the error be displayed nearby the related input or textarea?

[Wazzaps]

I chose to show it in the chooser since the form may be broken and I wouldn't want users to submit a broken form (because they will ignore the error) so I hide any form template with errors.
Also, this lets me show errors such "the 'name' field of the issue template are required".

[lunny]

Since #20987 merged, this PR could be rebased.

[delvh]

Or closed?

[Wazzaps]

I'll close this and open a new PR for any other enhancements :)