proxy.gzip.contenttype configures which responses should be compressed.
By default, responses sent to the client are not compressed even if the
client accepts compressed responses by setting the ‘Accept-Encoding: gzip’
header. By setting this value responses are compressed if the
header of the response matches and the response is not already compressed.
The list of compressable content types is defined as a regular expression.
The regular expression must follow the rules outlined in https://golang.org/pkg/regexp.
A typical example is
The default is