feat: add IAM role support and remove django.contrib.sites dependency

- Add optional IAM role authentication for AWS SES backend
- Remove AwsSesSettings model and sites framework dependency
- Maintain backward compatibility with access key authentication
- Update backend to conditionally use credentials when provided
- Remove sites framework from installation requirements
- Update documentation with IAM role configuration examples

BREAKING CHANGE: Removes django.contrib.sites dependency and AwsSesSettings model

README.md

@@ -70,14 +70,18 @@ SITE_ID = 1
 
 Configure AWS SES credentials and the email backend:
 
+### Option 1: IAM Role (Recommended for AWS environments)
 ```python
-AWS_SES_ACCESS_KEY_ID = 'your-access-key-id'  # Replace with your AWS IAM credentials
-AWS_SES_SECRET_ACCESS_KEY = 'your-secret-access-key'
-AWS_SES_REGION_NAME = 'us-east-1'  # Adjust to your AWS SES region
+# No AWS credentials needed in settings
+AWS_SES_REGION_NAME = 'us-east-1'
 AWS_SES_REGION_ENDPOINT = 'https://email.us-east-1.amazonaws.com'
-
 EMAIL_BACKEND = 'django_aws_ses.backends.SESBackend'
-DEFAULT_FROM_EMAIL = 'no-reply@yourdomain.com'  # Verified in AWS SES
+DEFAULT_FROM_EMAIL = 'no-reply@yourdomain.com'
+```
+### Option 2: Access Keys
+```
+AWS_SES_ACCESS_KEY_ID = 'your-access-key-id'
+AWS_SES_SECRET_ACCESS_KEY = 'your-secret-access-key'
 ```
 
 Optional: Enable debugging logs for troubleshooting: