Rewrite vso, rename to [AzureDevops], validate SVG [readthedocs]

[paulmelnikow]

This PR does a couple things:

1. Add validation to BaseSvgScrapingService and update readthedocs accordingly.
2. Rewrite vso and add more tests. Rename it internally to azure-devops. URLs are still /vso for now. Should we make a way to let a service register multiple URL patterns?
3. Handle shared code using a functional pattern instead of inheritance. This comes from a discussion [WIP] Rewrite [vso] badges #2031 (comment). I like the functional approach because it's more direct, nimble, and easy to reason about; plus it allows services to grow from a family of one to two more easily.

[shields-ci]

	Warnings
⚠️	This PR modified service code for readthedocs but not its test code. That's okay so long as it's refactoring existing code.

	Messages
📖	✨ Thanks for your contribution to Shields, @paulmelnikow!

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[chris48s]

Should we make a way to let a service register multiple URL patterns?

The way we've handled this on other badges is to stick the alternatives in a non-capturing group

e.g:

shields/services/wordpress/wordpress-rating.service.js

Lines 81 to 87 in 4a298cb

	static get url() {
	return {
	base: `wordpress/${extensionType}`,
	format: '(?:stars|r)/(.+)',
	capture: ['slug'],
	}
	}

so you could use (?:vso|azure-devops) to 'rebrand' the URLs /azure-devops but still allow /vso for backwards compatibility.

Handle shared code using a functional pattern instead of inheritance.

Seems reasonable 👍 Its a useful pattern to add to the toolbelt. I suspect its probably going to be most useful for larger service families where there is commonality but also variance as opposed to a rigid parent/child structure. I wouldn't particulary want to mandate style here though. Lets leave composition vs inheritance up to the implementer.

[paulmelnikow]

I suspect its probably going to be most useful for larger service families where there is commonality but also variance as opposed to a rigid parent/child structure.

Could be true. I could also see it being valuable for single-service families which grow larger over time.

[paulmelnikow]

Thanks for reviewing!

[shields-deployment]

This pull request was merged to master branch. This change is now waiting for deployment, which will usually happen within a few days. Stay tuned by joining our #ops channel on Discord!

After deployment, changes are copied to gh-pages branch: