F24_PROG1322_03.4_Step 4 - Nullable Foreign Key

We add a composite unique constraint and a new Model class in a 1:0 or m relationship to Patient.
1:00 Composite Unique Constraint
4:00 Add to Catch for DbUpdateException
8:15 Medical Trial Model
10:30 Nullable Foreign Key properties
11:40 DbContext - Cascade Delete?
13:35 Database Initializer
16:53 Seed Data
19:30 Changes to the UI
20:45 Modify Views
25:15 Controller Changes, Select Lists
28:45 .Include()
30:00 Add MedicalTrialID to White List
32:45 Use ToolTip instead of showing large text values
35:20 Style ToolTip - RenderSection