Added stroageUnit to contactType enum in db Schema

- contactInfo in StorageUnit is not optional anymore.

prisma/schema.prisma

@@ -67,10 +67,10 @@ model StorageLocation {
 /// A StorageUnit is the base and can hold multiple StorageLocations.
 model StorageUnit {
   id   Int    @id @default(autoincrement())
-  name String
+  name String @unique
 
-  contactInfo   contactInfo? @relation(fields: [contactInfoId], references: [id])
-  contactInfoId Int?
+  contactInfo   contactInfo @relation(fields: [contactInfoId], references: [id])
+  contactInfoId Int
 
   StorageLocation StorageLocation[]
 }
@@ -98,6 +98,7 @@ model contactInfo {
 }
 
 enum contactType {
+  storageUnit
   person
   customer
   company