Use a concrete struct for server.Create options.
Update the acceptance tests to match.
Use a struct for Update options, too.
Let's call it "ToServerXyzReqBody".
ReqBody -> Map
Use the global MaybeString function.
getXyzUrl -> xyzUrl
Use XyzResult structs and Extract methods.
Rework token creation to use Result structs and Extract.
create volume
change CreateOpts from structure to map to avoid default null values
delete volume
get volume
list volumes
create snapshot
delete snapshot
get snapshot
list snapshots
urls.go for block storage endpoints
remove client.go (functionality located elsewhere)