CanonicalMeta extract header name or its lowercase version.

FromContextCopy returns as COPY of the internal metadata, that can be subsequently modified.

FromContextRead returns internal metadata as is.

MinioMetaFromContext prepares metadata for minio client.

WithAdditionalMetadata retrieves existing meta, adds new key/values to the map and produces a new context It enforces case-conflicts on all keys.

WithUserNameMetadata appends a username to both the context metadata and as context key.