Replace #16455Close#21803
Mixing different Gitea contexts together causes some problems:
1. Unable to respond proper content when error occurs, eg: Web should
respond HTML while API should respond JSON
2. Unclear dependency, eg: it's unclear when Context is used in
APIContext, which fields should be initialized, which methods are
necessary.
To make things clear, this PR introduces a Base context, it only
provides basic Req/Resp/Data features.
This PR mainly moves code. There are still many legacy problems and
TODOs in code, leave unrelated changes to future PRs.
Remove `[repository.editor] PREVIEWABLE_FILE_MODES` setting that seemed
like it was intended to support this but did not work. Instead, whenever
viewing a file shows a preview, also have a Preview tab in the file
editor.
Add new `/markup` web and API endpoints with `comment`, `gfm`,
`markdown` and new `file` mode that uses a file path to determine the
renderer.
Remove `/markdown` web endpoint but keep the API for backwards and
GitHub compatibility.
## ⚠️ BREAKING ⚠️
The `[repository.editor] PREVIEWABLE_FILE_MODES` setting was removed.
This setting served no practical purpose and was not working correctly.
Instead a preview tab is always shown in the file editor when supported.
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Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
