refactor [cdnjs] integration

[chris48s]

Found some time to get stuck into some refactoring. Lets start small and work up :)

[shields-ci]

	Warnings
⚠️	This PR modified the server but none of the service tests. That's okay so long as it's refactoring existing code.
⚠️	This PR modified helper functions in lib/ but not accompanying tests. That's okay so long as it's refactoring existing code.

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[RedSparr0w]

👍

[RedSparr0w]

Nice work on this!

I was working on 1 the other week but got stuck as it had multiple regex, any idea how we would go about those badges?
eg: bitbucket & github

[chris48s]

I was working on 1 the other week but got stuck as it had multiple regex, any idea how we would go about those badges?

Think we started chucking some ideas about here: #1358 (comment)

Broadly, if we've got currently got a service integration and there's currently one function that does both a version badge and a downloads badge, we should split that into 2 classes.

If that means we've got duplication to deal with, common code than then be shared either by defining shared helper functions which we call in multiple classes, or maybe in some cases inheritance might be a good pattern e.g:

class BaseGitHubService extends BaseService {
  // shared code goes here
}

class GitHubDownloads extends BaseGitHubService {
  // bla
}

class GitHubVersion extends BaseGitHubService {
  // bla
}

..or something like that.

Hopefully that's what you meant. I'll try a service like that with several endpoints next. It will probably be easier to discuss once we've got a concrete example.