Enable / Disable scheduler job processing + provide Scheduler Status

[de-jcup]

At the moment a deployment in cluster environment - e.g. kubernetes - has got following problem:

When we a upgrade deployed server versions to next version, the running server instances will be stopped.... so also the JVMs... means also every running SecHub Job inside... After the new deployments these jobs are lost.

The easiest way to handle this, is to integrate a switch option into sechub administration and sechub scheduler.

Usecases:

• Admin stops scheduling
• Admin restarts scheduling
• Admin gets information about scheduling status (stopped,running, amount of waiting scheduled Jobs)

When sheduling is enabled/disabled a notification to admins shall be sent, so it's clear what happend (when disabled no job processing happens...)

[de-jcup]

We provide here now a common way for getting status information in administration - not only for scheduling but also for any other kind of status information. One start entry point: StatusAdministrationRestController

[de-jcup]

Found SecHubAdministrationEnvironment problematic, will rename SecHubServerEnvironment to SecHubEnvironment and make available in shared kernel.

Reason: We need the information about sechub server address very often and we have currently no email / notification where we use a special administration url. If we need this we should provide the administration url also inside SecHubEnvironment! Having multiple pods we can add the information inside kubernetes deployments as well in future!