Version top-level element
Top-level version property is defined by the specification for backward compatibility but is only informative.
A Compose implementation SHOULD NOT use this version to select an exact schema to validate the Compose file, but prefer the most recent schema at the time it has been designed.
Compose implementations SHOULD validate they can fully parse the Compose file. If some fields are unknown, typically because the Compose file was written with fields defined by a newer version of the specification, Compose implementations SHOULD warn the user. Compose implementations MAY offer options to ignore unknown fields (as defined by "loose" mode).