Support import from MySQL

Import to Chronos data model via MySQL and add new database fields to Chronos models.

• Teachers
• Classes
• Subjects
• Rooms
• Absence reasons
• Supervision areas
• Supervisions
• Lessons
• Substitutions
• Substitutions without lesson
• Absences
• Events
• Holidays
• Exams / Calendar [optional, include later]
• Atomic transactions
• Status bar
• Celery task

This is the only goal of the SchoolApps merge in this app, so after it is closed, the merge must be finished and the project clean.

changed title from Merge-Todos to Support import from MySQL

changed the description

assigned to @nik and unassigned @hansegucker

mentioned in issue AlekSIS-App-Chronos#58 (closed)

changed milestone to %2.0a1

mentioned in merge request !13 (merged)

changed milestone to %2.0a2

unassigned @nik

added part::backend prio::1 type::feature workflow::confirmed labels

assigned to @hansegucker

changed the description

marked the checklist item Teachers as completed

marked the checklist item Classes as completed

marked the checklist item Rooms as completed

marked the checklist item Subjects as completed

marked the checklist item Supervision areas as completed

marked the checklist item Supervisions as completed

marked the checklist item Lessons as completed

marked the checklist item Substitutions as completed

marked the checklist item Absence reasons as completed