# Functions
AppendToClientContext returns a new context with the provided kv merged with any existing metadata in the context.
FromClientContext returns the client metadata in ctx if it exists.
FromServerContext returns the server metadata in ctx if it exists.
MergeToClientContext merge new metadata into ctx.
New creates an MD from a given key-values map.
NewClientContext creates a new context with client md attached.
NewServerContext creates a new context with client md attached.
# Type aliases
Metadata is our way of representing request headers internally.