Refactoring auth package and move into API

Signed-off-by: Evgeniy Kulikov <kim@nspcc.ru>

api/auth/regexp-utils.go

@@ -0,0 +1,20 @@
+package auth
+
+import "regexp"
+
+type regexpSubmatcher struct {
+	re *regexp.Regexp
+}
+
+func (r *regexpSubmatcher) getSubmatches(target string) map[string]string {
+	matches := r.re.FindStringSubmatch(target)
+	l := len(matches)
+
+	sub := make(map[string]string, l)
+	for i, name := range r.re.SubexpNames() {
+		if i > 0 && i <= l {
+			sub[name] = matches[i]
+		}
+	}
+	return sub
+}