Allow admin to create "internal" events not displayed to all users

What does this MR do and why?

Allow admin to create "internal" events not displayed to all users

• feat(*.IncidentEvent): Allow to create internal IncidentEvent only visible when logged in (#40 (closed))
• feat(*.MaintenanceEvent): Allow to create internal MaintenanceEvent only visible when logged in (#40 (closed))

Implement #40 (closed)

Screenshots or screen recordings

MR acceptance checklist

• My code follows the style guidelines of this project
• I ran pylint 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
• My changes generate no new warnings
• My code needed automated testing. I have added them (this is optional task)