Merge most UI page size settings into one

[noerw]

Note: I'm opening this to gauge if there are actually instances out there that use different values for some of these settings.
→ 👎 reaction means you do, 👍 means you don't

---

the problem

There's problems with all these page size config settings:

• they are overly specific, lacking a use case
• although having very specific names, they are still used for multiple things (IssuePagingNum for issues, projects, milestones)
• they bloat the docs
• they are partly undocumented
• they have the same default value (at least as of Increase default item listing size ISSUE_PAGING_NUM to 20 #20547)
• they have a bad naming convention 😬

the proposal

Let's remove:

ExplorePagingNum:    20, // ui.EXPLORE_PAGING_NUM
SitemapPagingNum:    20, // ui.SITEMAP_PAGING_NUM
IssuePagingNum:      20, // ui.ISSUE_PAGING_NUM
RepoSearchPagingNum: 20, // ...
MembersPagingNum:    20,
FeedPagingNum:       20,
PackagesPagingNum:   20,

and replace with

PageSize: 20,

This would leave us with the following UI page size settings:

PageSize:            20,
FeedMaxCommitNum:    5,
GraphMaxCommitNum:   100,
CodeCommentLines:    4,
ReactionMaxUserNum:  10,

I'd say the complexity of providing backwards compat is not worth it, as the resulting breakage will be very minor.
Maybe we could maintain ISSUE_PAGING_NUM as deprecated fallback, that's the setting I've seen used most often (because it defaulted to 10 until #20547)

Screenshots

No response

[lunny]

But release page size should be different. We could have a default one which could be override by others.

[noerw]

Good pointer, that size is not among the list of settings to remove from the [ui] section.
Turns out there is another page size option in config section [repository.release] ([1]), which is the only frontend page size that is in a separate section.

Also, there's some code that makes use of the API page limits in the frontend ([1], [2]), this would also be good to clean up (either move the setting out of the API scope, or add a separate setting for UI).

• [1]
  

  gitea/routers/web/repo/release.go

  Lines 90 to 99 in 913b67f

  	listOptions := db.ListOptions{
  	Page: ctx.FormInt("page"),
  	PageSize: ctx.FormInt("limit"),
  	}
  	if listOptions.PageSize == 0 {
  	listOptions.PageSize = setting.Repository.Release.DefaultPagingNum
  	}
  	if listOptions.PageSize > setting.API.MaxResponseItems {
  	listOptions.PageSize = setting.API.MaxResponseItems
  	}

• [2]
  

  gitea/models/db/list_options.go

  Lines 83 to 95 in 913b67f

  	// NewAbsoluteListOptions creates a list option with applied limits
  	func NewAbsoluteListOptions(skip, take int) *AbsoluteListOptions {
  	if skip < 0 {
  	skip = 0
  	}
  	if take <= 0 {
  	take = setting.API.DefaultPagingNum
  	}
  	if take > setting.API.MaxResponseItems {
  	take = setting.API.MaxResponseItems
  	}
  	return &AbsoluteListOptions{skip, take}
  	}