LTI sections cannot be given Start and End dates

[halturner]

When creating a new LTI section, Start and End Dates are not automatically applied and they cannot be manually applied by the instructor or admin. This affects:

• ability to apply gating or scheduling
• Torus's "This project has X active course sections" feature
  
• the student's payment grace period
  
• general OLI recordkeeping
  

Desired behavior:

• both dates are required
• during either LTI or independent-section setup, date-entry would be a step that precedes creation
• dates can be updated by instructor or admin after course creation
  • if students have registered, updated dates should adjust some dependent grace period duration calculations
  • if the Start Date is moved BACKWARD, all existing grace period durations should remain unchanged; shortening their grace period duration may be unfair
  • if the Start Date is moved FORWARD, all existing grace periods should be adjusted by the same amount of time that the Start Date was adjusted

[darrensiegel]

The upfront requiring of start and end dates will be handled by https://eliterate.atlassian.net/browse/MER-1728

Need a ticket for allowing edit after creation.

[halturner]

Ticket for editing date after section creation has been opened.

[eliknebel]

fixed