fix(prisma): mark most brand fields as optional

This patch makes most of the brand fields optional. It is better that
these are left as NULL when importing brands than for me to set them to
something nonsensical. I will gradually populate these fields as
necessary, but their initial absence shouldn't block record creation.

prisma/migrations/20230725040705_make_most_brand_fields_optional/migration.sql

@@ -0,0 +1,5 @@
+-- AlterTable
+ALTER TABLE "Brand" ALTER COLUMN "description" DROP NOT NULL,
+ALTER COLUMN "companyId" DROP NOT NULL,
+ALTER COLUMN "countryId" DROP NOT NULL,
+ALTER COLUMN "tier" DROP NOT NULL;

prisma/schema.prisma

@@ -187,15 +187,15 @@ model Brand {
   url String? @unique
 
   // A short description of the brand, typically sourced from Wikipedia.
-  description String
+  description String?
 
-  // The brand's tier.
+  // The brand's tier. This will be NULL if it has not been assigned yet.
   // @todo perhaps rename this to "BrandTier" to avoid confusion with "Level"? 
-  tier Tier
+  tier Tier?
 
-  // The company that owns and operates the brand.
-  company   Company @relation(fields: [companyId], references: [id], onDelete: Cascade, onUpdate: Cascade)
-  companyId Int
+  // The company that owns and operates the brand (if known).
+  company   Company? @relation(fields: [companyId], references: [id], onDelete: Cascade, onUpdate: Cascade)
+  companyId Int?
 
   // The products designed or otherwise produced by the brand.
   products Product[]
@@ -218,9 +218,9 @@ model Brand {
   // The collections designed by the brand.
   collections Collection[]
 
-  // The country the brand purports to be from.
-  country   Country @relation(fields: [countryId], references: [id], onDelete: Cascade, onUpdate: Cascade)
-  countryId Int
+  // The country the brand purports to be from (if known).
+  country   Country? @relation(fields: [countryId], references: [id], onDelete: Cascade, onUpdate: Cascade)
+  countryId Int?
 }
 
 // A country is a sovereign state. Countries can have many brands and sizes.