Update aws-role config to aws-role-arn.

Summary -
1. Updated README.md
2. SigV4AuthProvider.java

Author: akshayar

README.md

@@ -69,7 +69,7 @@ One of the constructors for `software.aws.mcs.auth.SigV4AuthProvider` takes two
 
 ### Configuration
 
-Set the IAM Role explicitly in your `advanced.auth-provider` configuration (see example below), by specifying the `advanced.auth-provider.aws-role` property.
+Set the IAM Role explicitly in your `advanced.auth-provider` configuration (see example below), by specifying the `advanced.auth-provider.aws-role-arn` property.
 
 ## Add the Authentication Plugin to the Application
 
@@ -164,7 +164,7 @@ The following is an example of this config with an explicit role to be assumed.
             auth-provider = {
                 class = software.aws.mcs.auth.SigV4AuthProvider
                 aws-region = us-east-2
-                aws-role = "arn:aws:iam::ACCOUNT_ID:role/ROLE_NAME"
+                aws-role-arn = "arn:aws:iam::ACCOUNT_ID:role/ROLE_NAME"
             }
             ssl-engine-factory {
                 class = DefaultSslEngineFactory

src/main/java/software/aws/mcs/auth/SigV4AuthProvider.java

@@ -106,7 +106,7 @@ public SigV4AuthProvider() {
 
     private final static DriverOption REGION_OPTION = () -> "advanced.auth-provider.aws-region";
 
-    private final static DriverOption ROLE_OPTION = () -> "advanced.auth-provider.aws-role";
+    private final static DriverOption ROLE_OPTION = () -> "advanced.auth-provider.aws-role-arn";
 
     /**
      * This constructor is provided so that the driver can create

src/test/resources/keyspaces-reference-withrole.conf

@@ -12,7 +12,7 @@ datastax-java-driver {
                 auth-provider = {
                    class = software.aws.mcs.auth.SigV4AuthProvider
                    aws-region = ap-south-1
-                   aws-role = "arn:aws:iam::ACCOUNT_ID:role/keyspaces-act2-role"
+                   aws-role-arn = "arn:aws:iam::ACCOUNT_ID:role/keyspaces-act2-role"
                  }
             ssl-engine-factory {
                 class = DefaultSslEngineFactory