Function read 

pub fn read(id: &str, ims: &Image) -> Result<ImageSessionMetadata, MantaError>

Read the CFS-derived provenance metadata back from an IMS image.

id must match ims.id; this is a guard so callers can’t pass a mismatched image by accident.

Errors

• MantaError::NotFound if ims.id is None or does not equal id.
• MantaError::MissingField if any of the three manta.image_session.* keys is absent from ims.metadata.
• MantaError::SerdeError if the groups value is not a valid JSON array of strings.