feat: pass nullable into many-to-one custom relations

docs/docs/guides/developer-guide/custom-fields/index.mdx

@@ -988,6 +988,9 @@ In addition to the common properties, the `relation` custom fields have some typ
 - [`eager`](#eager)
 - [`graphQLType`](#graphqltype)
 - [`inverseSide`](#inverseside)
+- [`cascade`](#cascade)
+- [`onDelete`](#ondelete)
+- [`onUpdate`](#onupdate)
 
 #### entity
 
@@ -1102,6 +1105,94 @@ const { productReviews } = await this.connection.getRepository(ProductReview).fi
 });
 ```
 
+#### cascade
+
+<CustomFieldProperty required={false} type="boolean | ('insert' | 'update' | 'remove' | 'soft-remove' | 'recover')[]" />
+
+Whether to [cascade](https://typeorm.io/docs/relations/relations#cascade-options) operations on the relation. Defaults to `false`.
+
+```ts title="src/vendure-config.ts"
+import { Product } from '\@vendure/core';
+import { ProductReview } from './entities/product-review.entity';
+
+const config = {
+    // ...
+    customFields: {
+        Product: [
+            {
+                name: 'reviews',
+                list: true,
+                type: 'relation',
+                entity: ProductReview,
+                cascade: ['insert', 'update'], // [!code highlight]
+            },
+        ]
+    }
+};
+```
+
+#### onDelete
+<CustomFieldProperty required={false} type="'RESTRICT' | 'CASCADE' | 'SET NULL' | 'NO ACTION' | 'SET DEFAULT'" />
+
+The [onDelete](https://typeorm.io/docs/relations/relations/) behavior for the relation. Defaults to `NO ACTION`.
+
+:::note
+
+Setting `onDelete` to `CASCADE` or `cascade: ['remove']` means that if the referenced entity is deleted, rows owning this relation may also be deleted.
+This can have unintended consequences, especially when referencing core Vendure entities.
+For example, if you have a relation to `ProductVariant` and set `onDelete: 'CASCADE'`, deleting that `ProductVariant` can cascade to rows that reference it.
+Use with caution.
+
+Setting `onDelete` on a `ManyToMany` (`list: true`) relation will affect the join table, but not the related entity.
+
+```ts title="src/vendure-config.ts"
+import { Product } from '\@vendure/core';
+import { ProductReview } from './entities/product-review.entity';
+
+const config = {
+    // ...
+    customFields: {
+        Product: [
+            {
+                name: 'reviews',
+                list: false,
+                type: 'relation',
+                entity: ProductReview,
+                onDelete: 'SET NULL', // [!code highlight]
+            },
+        ]
+    }
+};
+```
+
+#### onUpdate
+<CustomFieldProperty required={false} type="'RESTRICT' | 'CASCADE' | 'SET NULL' | 'NO ACTION' | 'SET DEFAULT'" />
+
+The [onUpdate](https://typeorm.io/docs/relations/relations/) behavior for the relation. If not set, the database default (`NO ACTION`) applies.
+`onUpdate` is not supported by SQLite and will be ignored if you are using SQLite as your database.
+
+Setting `onUpdate` on a `ManyToMany` (`list: true`) relation will affect the join table, but not the related entity.
+
+```ts title="src/vendure-config.ts"
+import { Product } from '\@vendure/core';
+import { ProductReview } from './entities/product-review.entity';
+
+const config = {
+    // ...
+    customFields: {
+        Product: [
+            {
+                name: 'reviews',
+                list: false,
+                type: 'relation',
+                entity: ProductReview,
+                onUpdate: 'CASCADE', // [!code highlight]
+            },
+        ]
+    }
+};
+```
+
 ## Custom Field UI
 
 In the Dashboard, an appropriate default form input component is used for each custom field type. The Dashboard comes with a set of ready-made form input components, but it is also possible to create custom form input components. The ready-made components are:

docs/docs/reference/typescript-api/custom-fields/typed-custom-single-field-config.mdx

@@ -2,7 +2,7 @@
 title: "TypedCustomSingleFieldConfig"
 generated: true
 ---
-<GenerationInfo sourceFile="packages/core/src/config/custom-field/custom-field-types.ts" sourceLine="101" packageName="@vendure/core" />
+<GenerationInfo sourceFile="packages/core/src/config/custom-field/custom-field-types.ts" sourceLine="102" packageName="@vendure/core" />
 
 Configures a custom field on an entity in the [CustomFields](/reference/typescript-api/custom-fields/#customfields) config object.
 

packages/core/src/config/custom-field/custom-field-types.ts

@@ -28,6 +28,7 @@ import {
     Type,
     UiComponentConfig,
 } from '@vendure/common/lib/shared-types';
+import { RelationOptions } from 'typeorm';
 
 import { RequestContext } from '../../api/common/request-context';
 import { Injector } from '../../common/injector';
@@ -114,9 +115,10 @@ export type TypedCustomSingleFieldConfig<
 export type TypedCustomListFieldConfig<
     T extends CustomFieldType,
     C extends CustomField,
-> = BaseTypedCustomFieldConfig<T, C> & {
+> = Omit<BaseTypedCustomFieldConfig<T, C>, 'nullable'> & {
     list?: true;
     defaultValue?: Array<DefaultValueType<T>>;
+    nullable?: never;
     validate?: (
         value: Array<DefaultValueType<T>>,
     ) => string | LocalizedString[] | void | Promise<string | LocalizedString[] | void>;
@@ -149,9 +151,8 @@ export type RelationCustomFieldConfig = TypedCustomFieldConfig<
 > & {
     entity: Type<VendureEntity>;
     graphQLType?: string;
-    eager?: boolean;
     inverseSide?: string | ((object: any) => any);
-};
+} & Pick<RelationOptions, 'cascade' | 'onDelete' | 'onUpdate' | 'eager'>;
 
 // Struct field definitions
 export type BaseTypedStructFieldConfig<T extends StructFieldType, C extends GraphQLStructField> = Omit<