fix: make metadata key's constants

src/decorators.ts

@@ -1,15 +1,18 @@
 import type { ServiceIdentifier } from './types.js';
 
+export const DI_PARAM_TYPES = 'di:paramtypes';
+export const DI_INJECTABLE = 'di:injectable';
+
 export function inject<T>(serviceType: ServiceIdentifier<T>): ParameterDecorator {
   // eslint-disable-next-line @typescript-eslint/no-wrapper-object-types
   return (target: Object, _: string | symbol | undefined, parameterIndex: number) => {
-    Reflect.defineMetadata('di:paramtypes', serviceType, target, parameterIndex.toString());
+    Reflect.defineMetadata(DI_PARAM_TYPES, serviceType, target, parameterIndex.toString());
   };
 }
 
 export function injectable(): ClassDecorator {
   // eslint-disable-next-line @typescript-eslint/no-unsafe-function-type
   return (target: Function) => {
-    Reflect.defineMetadata('di:injectable', true, target);
+    Reflect.defineMetadata(DI_INJECTABLE, true, target);
   };
 }

src/serviceProvider.ts

@@ -1,3 +1,4 @@
+import { DI_PARAM_TYPES } from './decorators.js';
 import type {
   IServiceProvider,
   IServiceScope,
@@ -93,7 +94,7 @@ export class ServiceProvider implements IServiceProvider {
 
     const params = paramTypes.map((_: unknown, index: number) => {
       const serviceType = Reflect.getMetadata(
-        'di:paramtypes',
+        DI_PARAM_TYPES,
         ctor,
         index.toString(),
       ) as ServiceIdentifier<unknown>;