New notification provider: SMS Partner API

[nicolasverlhiac]

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Description

This adds the support for SmsPartner.fr in order to send SMS notifications in 200+ countries.

Type of change

Please delete any options that are not relevant.

• New feature (non-breaking change which adds functionality)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas (including JSDoc for methods)
• My changes generates no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

Event	Before	After
UP	-
DOWN	-
Certificate-expiry	-	-
Testing	-

[CommanderStorm]

Looks overall good.
I have left a few UX/i18n-comments below

[nicolasverlhiac]

Thank you so much @CommanderStorm for your review, it's much appreciated! :)

[CommanderStorm]

• Thinking about it: lets use a scoped key. The english translation for multiple numbers must be separated by is too specific to be usefull for other monitors ^^

[CommanderStorm]

Thanks for the new notification provider! 🎉

Note

This PR is part of the v2.0 merge window => see #4500 for the bugs that need to be addressed before we can ship this release ^^

_{All changes in this PR are small and uncontroversial ⇒ merging with junior maintainer approval}