fix(core): improve support for mapping DecimalType to number

docs/docs/custom-types.md

@@ -383,6 +383,18 @@ id3: number;
 
 > JavaScript cannot represent all the possible values of a `bigint` when mapping to the `number` type - only values up to `Number.MAX_SAFE_INTEGER` (2^53 - 1) are safely supported.
 
+### DecimalType
+
+DecimalType represents a `decimal` or `numeric` column type. By default, it maps to a JS `string`, as mapping it to `number` could result is precision lost. If you are fine with that, you can force mapping to a `number` with its constructor (just like with the `BigIntType`).
+
+```ts
+@Property({ type: DecimalType })
+price1: string;
+
+@PrimaryKey({ type: new DecimalType('number') })
+price2: number;
+```
+
 ### BlobType
 
 Blob type can be used to store binary data in the database.

packages/core/src/types/DecimalType.ts

@@ -7,8 +7,12 @@ import type { EntityProperty } from '../typings';
  */
 export class DecimalType extends Type<string | number, string> {
 
+  constructor(public mode?: 'number' | 'string') {
+    super();
+  }
+
   override convertToJSValue(value: string): number | string {
-    if (this.prop?.runtimeType === 'number') {
+    if ((this.mode ?? this.prop?.runtimeType) === 'number') {
       return +value;
     }
 
@@ -20,7 +24,7 @@ export class DecimalType extends Type<string | number, string> {
   }
 
   override compareAsType(): string {
-    return this.prop?.runtimeType ?? 'string';
+    return this.mode ?? this.prop?.runtimeType ?? 'string';
   }
 
 }