clarify in documentation cut-prefix meaning for middlewares header extraction

Author: aldas

middleware/extractor.go

@@ -66,6 +66,11 @@ func createExtractors(lookups string, authScheme string) ([]ValuesExtractor, err
 }
 
 // valuesFromHeader returns a functions that extracts values from the request header.
+// valuePrefix is parameter to remove first part (prefix) of the extracted value. This is useful if header value has static
+// prefix like `Authorization: <auth-scheme> <authorisation-parameters>` where part that we want to remove is `<auth-scheme> `
+// note the space at the end. In case of basic authentication `Authorization: Basic <credentials>` prefix we want to remove
+// is `Basic `. In case of JWT tokens `Authorization: Bearer <token>` prefix is `Bearer `.
+// If prefix is left empty the whole value is returned.
 func valuesFromHeader(header string, valuePrefix string) ValuesExtractor {
 	prefixLen := len(valuePrefix)
 	// standard library parses http.Request header keys in canonical form but we may provide something else so fix this

middleware/jwt.go

@@ -69,6 +69,11 @@ type (
 		// Optional. Default value "header:Authorization".
 		// Possible values:
 		// - "header:<name>" or "header:<name>:<cut-prefix>"
+		// 			`<cut-prefix>` is argument value to cut/trim prefix of the extracted value. This is useful if header
+		//			value has static prefix like `Authorization: <auth-scheme> <authorisation-parameters>` where part that we
+		//			want to cut is `<auth-scheme> ` note the space at the end.
+		//			In case of JWT tokens `Authorization: Bearer <token>` prefix we cut is `Bearer `.
+		// If prefix is left empty the whole value is returned.
 		// - "query:<name>"
 		// - "param:<name>"
 		// - "cookie:<name>"

middleware/key_auth.go

@@ -17,6 +17,10 @@ type (
 		// Optional. Default value "header:Authorization".
 		// Possible values:
 		// - "header:<name>" or "header:<name>:<cut-prefix>"
+		// 			`<cut-prefix>` is argument value to cut/trim prefix of the extracted value. This is useful if header
+		//			value has static prefix like `Authorization: <auth-scheme> <authorisation-parameters>` where part that we
+		//			want to cut is `<auth-scheme> ` note the space at the end.
+		//			In case of basic authentication `Authorization: Basic <credentials>` prefix we want to remove is `Basic `.
 		// - "query:<name>"
 		// - "form:<name>"
 		// - "cookie:<name>"