Support both general and specific date formatting

[djplaner]

Is your feature request related to a problem? Please describe.

Including dates for modules is a useful design feature, however, the current feature is very specific. Shortcomings include

1. No way to modify which specific "calendar" is used for specific dates beyond modifying code.
2. No way to use normal dates (i.e. not specific to a particularly university calendar)

Describe the solution you'd like

Collections should support some/all of the following

1. Teacher can use a standard calendar to specify dates for modules
2. Teacher can modify the start date of specific calendar and have all the other dates changed by the same time period, maintaining the relative distance with the start date
3. Teacher can choose to use a specific university calendar if one exists.

Use of the standard calendar would be the default model for Collections. The option for a specific calendar would only appear if that existed in the code base.

For example

The standard calendar function would combine ways to

1. Specify a module date (range) using standard calendar; and,
2. Update all the Collections' dates for a course by a fixed period. e.g.  Collections would find the earliest date currently set in Collections. The teacher could choose a new start date (either explicitly moving from Feb 3 to Jul 5) or specifying a time period. NOTE: This wouldn't help with the different placement of mid-semester breaks that can vary
3. Collections would update all the other dates by the same time period
4. The teacher can then modify if/when needed 
5. Idea of supporting both specific and generic dates

[djplaner]

Experimentation - sl-input type="date"

Shoelace's input component supports type=date for a functioning date picker. Could this be the replacement

• [x] Can it be easily included
• [ ] Can it be set externally (i.e. when a university standard date is chosen)
  • [ ] Yes, the format needs to be yyyy-MM-dd

[djplaner]

Moving into #248