branch_slug in ApplicationSet PR generator truncates too far

[whitelancer]

Hi there, I've noticed an issue with the branch_slug in the PR ApplicationSet generator that I'm hoping we can address. Since the library is using the Go slug library ("github.com/gosimple/slug") the default behavior is to have EnableSmartTruncate enabled/on. This creates a lot of problems when trying to generate unique branch names from long branches, such as:

	slug.MaxLength = 50
	urlSlug := slug.Make("feature/123reallylong/name/herethatmustbe/truncated/soon/orelseitwillblow/up")
	fmt.Println(urlSlug)

feature-123reallylong-name-herethatmustbe

And a bigger issue with a branch that only contains one slash (or hyphen):

	urlSlug = slug.Make("feature/123reallylongnameherethatmustbetruncatedsoonorelseitwillblowup")
	fmt.Println(urlSlug)

feature

When trying to use branch_slug to generate a container image name, this becomes a major problem especially in the second example. Here is what I expect and is more repeatable for other tools:

	slug.EnableSmartTruncate = false
	slug.MaxLength = 50
	urlSlug := slug.Make("feature/123reallylong/name/herethatmustbe/truncated/soon/orelseitwillblow/up")
	fmt.Println(urlSlug)

feature-123reallylong-name-herethatmustbe-truncate

	slug.EnableSmartTruncate = false
	urlSlug = slug.Make("feature/123reallylongnameherethatmustbetruncatedsoonorelseitwillblowup")
	fmt.Println(urlSlug)

feature-123reallylongnameherethatmustbetruncatedso

The simplest fix would be to disable smart truncate in the go library. I realize this may cause problems with existing params, but it's impossible to generate unique branch slugs when using smart truncate.

For instance, these all give back feature as the slug.

slug.EnableSmartTruncate = true
slug.MaxLength = 50
fmt.Println(slug.Make("feature/reallylongnamethatwillbetruncatedbecauseitistoolong"))
fmt.Println(slug.Make("feature/isanotherreallylongnamethatwillbetruncatedbadly"))
fmt.Println(slug.Make("feature/shouldbedifferentbutitalsoisnottruncatedcorrectly"))

[crenshaw-dev]

Cross-linking my answer from another thread: #10622 (comment)

[Aym3nTN]

This MR #15188 should've closed this one