changed notification.config from varchar to text.

[FJBlok]

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Description

I've changed the way a monitor config is stored in the database.
This was a varchar and now it is a text record. This will increase the length of the record you can store in that field.
I ran into an issue with ntfy(push notification service) that the config json was to big for that field.
Also this was marked as TODO in the code.

Type of change

• Bug fix (non-breaking change which fixes an issue)

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 generate no new warnings
• My code needed automated testing. I have added them (this is optional task)

[louislam]

Thanks, almost forget it. It is for 2.0.0.
Will add another pr for 1.23.3 maybe, since 1.23.x is using sql files to patch the database.