Add a new backup provider

Creates a new backup provider with the specified configuration. This endpoint supports various storage types including AWS S3, Azure Storage, Google Cloud Storage, S3-compatible storage, SFTP, and internal cloudpepper storage. The provider will be validated before being added to ensure connectivity and proper configuration.

Key Parameters:

• type: The storage provider type (e.g., 'aws_s3', 'azure', 'cloudpepper', 'google_cloud', 's3', 'sftp')
• secret: Authentication secret for the provider (e.g., AWS secret key, SFTP password/key)
• config: Provider-specific configuration parameters

NOTE: After adding a backup provider, you can use it to store backups of your Odoo instances. You can set a provider as the default for automatic backups via the set-default endpoint.