Fact Plugin: error handling

Current Situation
When an error occurs in the FactPlugin plugin:

• FactPlugin sends an email with the full error stacktrace when the JobScheduler is configured to send email on error
• FactPlugin logs this error and the full error stacktrace to a log file
• FactPlugin not sends a recovery email

When an error reoccurs (e.g. the connection to the reporting database can't be established) in the FactPlugin plugin:

• Email and log flooding when the database connection was not established immediately

Desired Behaviour
FactPlugin should:

• sends an email when the JobScheduler is configured to send email on error
• repeatable errors
  • sends the first error email immediately and logs the error with the full error stacktrace
  • all reoccurred errors will be logs immediately without the stacktrace
  • all reoccurred errors will be sended with the full error stacktrace if the interval of 5 minutes was reached
  • a recovery email with the full error stacktrace will be sended immediately
• non repeatable errors
  • sends and logs the message with the full error stacktrace immediately 
  • sends a recovery email with the full error stacktrace immediately

Test instructions

• JobScheduler is configured to send emails on error
• use the different DBMS, e.g:
  • MSSQL - JobScheduler database
  • MySQL - Reporting database
• start any "long running" job chain
  • configured e.g. with 2 steps and the execution time of each step ~ 5 seconds
• stop the Reporting database service after the job chain start
  • Test 1
    • start the Reporting database service after 1 minutes
  • Test 2
    • start the Reporting database service after 5 minutes
• * check the email and the log messages