Update mainframe file content by ID

Updates the content of an existing mainframe file by its unique file ID with new file content.

Process Overview:

1. Request Validation - Validates file ID and multipart file content
2. File Content Update - Updates the file with new multipart content

Key Features:

• Replace entire file content in a single operation
• Preserves file metadata and timestamps

Use Cases:

• Update script content from file
• Modify configuration files with new versions
• Replace file content without recreating

Required Permissions: replication-pipeline::update when permission harmonization is enabled; otherwise, replication-pipeline::manage.