Fix CustomConfigPath parameter indentation and regex pattern

- Fixed YAML indentation for CustomConfigPath parameter properties
- Corrected AllowedPattern regex to include proper escaping and end anchor
- Resolves CloudFormation validation error about null values

Author: EC2 Default User

template.yaml

@@ -147,13 +147,13 @@ Parameters:
   # Custom Configuation Path:
 
   CustomConfigPath:
-  Type: String
-  Default: ""
-  Description: >-
+    Type: String
+    Default: ""
+    Description: >-
       S3 URI pointing to your custom configuration YAML file. When provided, this configuration overrides the selected pattern preset and applies to all processing patterns. 
       Leave blank to use the selected pattern configuration preset. For example s3://my-bucket/custom-config/config.yaml
-  AllowedPattern: '^(|s3://[a-zA-Z0-9.\-_]+(/.*)?)'
-  ConstraintDescription: Must be empty or a valid S3 URI (e.g., s3://my-bucket/custom-config/config.yaml)
+    AllowedPattern: '^(|s3://[a-zA-Z0-9.\\-_]+(/.*)?)$'
+    ConstraintDescription: Must be empty or a valid S3 URI (e.g., s3://my-bucket/custom-config/config.yaml)
 
   # HITL (A2I) Configuration