Refactor server status and health

[samuelwei]

Fixes #652

Type (Highlight the corresponding type)

• Bugfix
• Feature
• Documentation
• Refactoring (e.g. Style updates, Test implementation, etc.)
• Other (please describe):

Checklist

• Code updated to current develop branch head
• Passes CI checks
• Is a part of an issue
• Tests added for the bugfix or newly implemented feature, describe below why if not
• Changelog is updated
• Documentation of code and features exists

Changes

• Add server status "draining": The server should not be used for sheduling (no new meetings), as soon as all meetings are finished, changed to disabled, still collect data for attandace, statistics, etc.
• Added server health [Online, Unhealthy, Offline]: Calculated by and error and revover counter according to the alogithm proposed by @defnull in BBB-Meeting disconnected from PILOS during network issues #652 (comment) configurable by BBB_SERVER_HEALTHY_THRESHOLD and BBB_SERVER_UNHEALTHY_THRESHOLD
• Add messages to users showing the reconnection progress
• End detached meetings after connection to server is restored
• Show server connection status in server list

Other information

[codecov]

Codecov Report

Attention: Patch coverage is 94.94382% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 95.80%. Comparing base (ae6b9e4) to head (2543018).
Report is 4 commits behind head on develop.

Files	Patch %	Lines
app/Console/Kernel.php	0.00%	6 Missing ⚠️
app/Services/ServerService.php	96.55%	3 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #911      +/-   ##
=============================================
+ Coverage      95.64%   95.80%   +0.16%     
- Complexity      1041     1074      +33     
=============================================
  Files            176      176              
  Lines           3763     3815      +52     
=============================================
+ Hits            3599     3655      +56     
+ Misses           164      160       -4     

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