feat: upload hasmany (#7796)

Supports `hasMany` upload fields, similar to how `hasMany` works in
other fields, i.e.:

```ts
{
  type: 'upload',
  relationTo: 'media',
  hasMany: true
}
```

---------

Co-authored-by: Jacob Fletcher <jacobsfletch@gmail.com>
Co-authored-by: James <james@trbl.design>

packages/db-mongodb/src/models/buildSchema.ts

@@ -595,14 +595,77 @@ const fieldToSchemaMap: Record<string, FieldSchemaGenerator> = {
     config: SanitizedConfig,
     buildSchemaOptions: BuildSchemaOptions,
   ): void => {
-    const baseSchema = {
-      ...formatBaseSchema(field, buildSchemaOptions),
-      type: mongoose.Schema.Types.Mixed,
-      ref: field.relationTo,
+    const hasManyRelations = Array.isArray(field.relationTo)
+    let schemaToReturn: { [key: string]: any } = {}
+
+    if (field.localized && config.localization) {
+      schemaToReturn = {
+        type: config.localization.localeCodes.reduce((locales, locale) => {
+          let localeSchema: { [key: string]: any } = {}
+
+          if (hasManyRelations) {
+            localeSchema = {
+              ...formatBaseSchema(field, buildSchemaOptions),
+              _id: false,
+              type: mongoose.Schema.Types.Mixed,
+              relationTo: { type: String, enum: field.relationTo },
+              value: {
+                type: mongoose.Schema.Types.Mixed,
+                refPath: `${field.name}.${locale}.relationTo`,
+              },
+            }
+          } else {
+            localeSchema = {
+              ...formatBaseSchema(field, buildSchemaOptions),
+              type: mongoose.Schema.Types.Mixed,
+              ref: field.relationTo,
+            }
+          }
+
+          return {
+            ...locales,
+            [locale]: field.hasMany
+              ? { type: [localeSchema], default: formatDefaultValue(field) }
+              : localeSchema,
+          }
+        }, {}),
+        localized: true,
+      }
+    } else if (hasManyRelations) {
+      schemaToReturn = {
+        ...formatBaseSchema(field, buildSchemaOptions),
+        _id: false,
+        type: mongoose.Schema.Types.Mixed,
+        relationTo: { type: String, enum: field.relationTo },
+        value: {
+          type: mongoose.Schema.Types.Mixed,
+          refPath: `${field.name}.relationTo`,
+        },
+      }
+
+      if (field.hasMany) {
+        schemaToReturn = {
+          type: [schemaToReturn],
+          default: formatDefaultValue(field),
+        }
+      }
+    } else {
+      schemaToReturn = {
+        ...formatBaseSchema(field, buildSchemaOptions),
+        type: mongoose.Schema.Types.Mixed,
+        ref: field.relationTo,
+      }
+
+      if (field.hasMany) {
+        schemaToReturn = {
+          type: [schemaToReturn],
+          default: formatDefaultValue(field),
+        }
+      }
     }
 
     schema.add({
-      [field.name]: localizeSchema(field, baseSchema, config.localization),
+      [field.name]: schemaToReturn,
     })
   },
 }