feat: header based acls (#337)

* feat: add header decoder

* feat: allow for dash substitute over slash for environments like kubernetes

* feat: use decoded headers in proxy controller

* refactor: simplify decode header to node function

* refactor: use stdlib prefix check in header decoder

* fix: lowercase key and filter before comparing

internal/utils/decoders/header_decoder_test.go

@@ -0,0 +1,73 @@
+package decoders_test
+
+import (
+	"reflect"
+	"testing"
+	"tinyauth/internal/config"
+	"tinyauth/internal/utils/decoders"
+)
+
+func TestDecodeHeaders(t *testing.T) {
+	// Variables
+	expected := config.AppConfigs{
+		Apps: map[string]config.App{
+			"foo": {
+				Config: config.AppConfig{
+					Domain: "example.com",
+				},
+				Users: config.AppUsers{
+					Allow: "user1,user2",
+					Block: "user3",
+				},
+				OAuth: config.AppOAuth{
+					Whitelist: "somebody@example.com",
+					Groups:    "group3",
+				},
+				IP: config.AppIP{
+					Allow:  []string{"10.71.0.1/24", "10.71.0.2"},
+					Block:  []string{"10.10.10.10", "10.0.0.0/24"},
+					Bypass: []string{"192.168.1.1"},
+				},
+				Response: config.AppResponse{
+					Headers: []string{"X-Foo=Bar", "X-Baz=Qux"},
+					BasicAuth: config.AppBasicAuth{
+						Username:     "admin",
+						Password:     "password",
+						PasswordFile: "/path/to/passwordfile",
+					},
+				},
+				Path: config.AppPath{
+					Allow: "/public",
+					Block: "/private",
+				},
+			},
+		},
+	}
+	test := map[string]string{
+		"Tinyauth-Apps-Foo-Config-Domain":                   "example.com",
+		"Tinyauth-Apps-Foo-Users-Allow":                     "user1,user2",
+		"Tinyauth-Apps-Foo-Users-Block":                     "user3",
+		"Tinyauth-Apps-Foo-OAuth-Whitelist":                 "somebody@example.com",
+		"Tinyauth-Apps-Foo-OAuth-Groups":                    "group3",
+		"Tinyauth-Apps-Foo-IP-Allow":                        "10.71.0.1/24,10.71.0.2",
+		"Tinyauth-Apps-Foo-IP-Block":                        "10.10.10.10,10.0.0.0/24",
+		"Tinyauth-Apps-Foo-IP-Bypass":                       "192.168.1.1",
+		"Tinyauth-Apps-Foo-Response-Headers":                "X-Foo=Bar,X-Baz=Qux",
+		"Tinyauth-Apps-Foo-Response-BasicAuth-Username":     "admin",
+		"Tinyauth-Apps-Foo-Response-BasicAuth-Password":     "password",
+		"Tinyauth-Apps-Foo-Response-BasicAuth-PasswordFile": "/path/to/passwordfile",
+		"Tinyauth-Apps-Foo-Path-Allow":                      "/public",
+		"Tinyauth-Apps-Foo-Path-Block":                      "/private",
+	}
+
+	// Test
+	result, err := decoders.DecodeHeaders(test)
+
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	if !reflect.DeepEqual(expected, result) {
+		t.Fatalf("Expected %v but got %v", expected, result)
+	}
+}