Resolve "Changing the date of a slotted lab does not move the slots"

What does this mr do?

If a slotted lab is edited, it's slots won't update since they are represented by a Slot which has a fixed start and end. This needs to be switched to an offset based on the start of the lab. `

Actions taken to fix bug

Added a new offsetSequence number to denote the position of a slot within a slotted lab. The reason we did not get rid of the slot from the timeslot completely, was that it did not work with QueryDSL.

Screenshots

Before Change:

After Change:

Note that this MR does not support a change in the length of the lab whilst the offset changes. This will be addressed in another MR.

Does this MR meet the acceptance criteria?

• I have added a changelog entry to reflect the significant changes I made and the bug I fixed.
• A test was created to test the bug.
• I have updated the documentation accordingly.
• I adhere to the style guide.