feat(#31): implemented api for environment crud operations

backend/src/models/secret.ts

@@ -2,10 +2,6 @@ import { Schema, model, Types } from 'mongoose';
 import {
 	SECRET_SHARED,
 	SECRET_PERSONAL,
-	ENV_DEV,
-	ENV_TESTING,
-	ENV_STAGING,
-	ENV_PROD
 } from '../variables';
 
 export interface ISecret {
@@ -53,7 +49,6 @@ const secretSchema = new Schema<ISecret>(
 		},
 		environment: {
 			type: String,
-			enum: [ENV_DEV, ENV_TESTING, ENV_STAGING, ENV_PROD],
 			required: true
 		},
 		secretKeyCiphertext: {