Deprecate DefaultCredentialsProvider.create() due to singleton issues (#6166)

* Deprecate DefaultCredentialsProvider.create() due to singleton issues

* Add deprecation notice to create() method
* Update documentation to clearly explain the risks
* Recommend using builder().build() instead

* Update bugfix-AWSSDKforJavav2-c5cff7a.json

Author: jencymaryjoseph

.changes/next-release/bugfix-AWSSDKforJavav2-c5cff7a.json

@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "AWS SDK for Java v2",
+    "contributor": "jencymaryjoseph",
+    "description": "Deprecated DefaultCredentialsProvider.create() since it creates Singleton instance"
+}

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/DefaultCredentialsProvider.java

@@ -74,10 +74,15 @@ private DefaultCredentialsProvider(Builder builder) {
     }
 
     /**
-     * Returns the singleton instance of the {@link DefaultCredentialsProvider} using the default configuration. 
-     * Configuration can be specified by creating an instance using the {@link #builder()}. If you want to 
+     * Returns the singleton instance of the {@link DefaultCredentialsProvider} using the default configuration.
+     * Configuration can be specified by creating an instance using the {@link #builder()}. If you want to
      * create a new instance, use {@link #builder()} instead.
+     *
+     * @deprecated The create() method that returns a singleton instance which can cause issues if one client closes the provider
+     * while others are still using it. Use {@link #builder().build()} to create independent instances, which is the
+     * safer approach and recommended for most use cases.
      */
+    @Deprecated
     public static DefaultCredentialsProvider create() {
         return DEFAULT_CREDENTIALS_PROVIDER;
     }