feat(api): implement new api handler

pkg/api/middleware/require_token.go

@@ -0,0 +1,24 @@
+package middleware
+
+import (
+	"fmt"
+	. "github.com/containrrr/watchtower/pkg/api/prelude"
+)
+
+// RequireToken returns a prelude.Middleware that checks token validity
+func RequireToken(token string) Middleware {
+	return func(next HandlerFunc) HandlerFunc {
+		want := fmt.Sprintf("Bearer %s", token)
+		return func(c *Context) Response {
+			auth := c.Request.Header.Get("Authorization")
+			if auth == "" {
+				return Error(ErrMissingToken)
+			}
+
+			if auth != want {
+				return Error(ErrInvalidToken)
+			}
+			return next(c)
+		}
+	}
+}