feat(checker): port other checkers over

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/checker/headermatches/checker.go

@@ -0,0 +1,24 @@
+package headermatches
+
+import (
+	"net/http"
+	"regexp"
+)
+
+type Checker struct {
+	header string
+	regexp *regexp.Regexp
+	hash   string
+}
+
+func (c *Checker) Check(r *http.Request) (bool, error) {
+	if c.regexp.MatchString(r.Header.Get(c.header)) {
+		return true, nil
+	}
+
+	return false, nil
+}
+
+func (c *Checker) Hash() string {
+	return c.hash
+}