Add a public URL field for monitors and uses it on the status page

[Ionys320]

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Description

Fixes #2507

Allows to set a public URL for each monitor, and use this URL as the clickable URL for the status page instead of the default/monitor URL. Cf #2507 who explains better than me!

Type of change

Please delete any options that are not relevant.

• User interface (UI)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

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)