* Implemented health check notifier as a hosted service.
Added validation to health check settings.
* Registered health check notifier as a hosted service.
Modified health check nested settings to use concrete classes to align with other configuration models.
* Resolved issues with email sending using development server.
* PR review comments and fixed failing unit test.
* Changed period and delay millisecond and hourly values to TimeSpans.
Changed configuration of first run time for health check notifications to use H:mm format.
* Set up SecureSocketOptions as a locally defined enum.
* Tightened up time format validation to verify input is an actual time (with hours and minutes only) and not a timespan.
* Aligned naming and namespace of health check configuration related classes with other configuration classes.
* Created constants for hex colors used in formatting health check results as HTML.
* Revert "Tightened up time format validation to verify input is an actual time (with hours and minutes only) and not a timespan."
This reverts commit f9bb8a7a825bcb58146879f18b47922e09453e2d.
* Renamed method to be clear validation is of a TimeSpan and not a time.
Co-authored-by: Bjarke Berg <mail@bergmania.dk>
