Remove hardcoded secret key from this PR

Author: MD-Suhad

src/main/resources/application.yml

@@ -1,8 +1,8 @@
 spring:
   datasource:
     url: jdbc:mysql://localhost:3306/blogapi?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC
-    username: root
-    password: ??@@suhad@@??
+    username: ${DB_USERNAME}
+    password: ${DB_PASSWORD}
   jpa:
     hibernate:
       ddl-auto: update