fix(types): uniqueKey support for BelongsToManyOptions interface (#10751)

types/lib/associations/belongs-to-many.d.ts

@@ -67,6 +67,11 @@ export interface BelongsToManyOptions extends ManyToManyOptions {
    * Should the join model have timestamps
    */
   timestamps?: boolean;
+  
+  /**
+   * The unique key name to override the autogenerated one when primary key is not present on through model
+   */
+  uniqueKey?: string;
 }
 
 export class BelongsToMany<S extends Model = Model, T extends Model = Model> extends Association<S, T> {