Add initial implementation of gitea-mcp-forward-auth microservice

- Create build and release workflows for CI/CD
- Implement Dockerfile for multi-stage builds
- Add core authentication logic with token validation
- Include HTTP handler for authorization checks
- Set up Kubernetes deployment and service manifests
- Update README with usage instructions and configuration details

internal/auth/auth_test.go

@@ -0,0 +1,87 @@
+package auth
+
+import "testing"
+
+func TestValidator_IsValid(t *testing.T) {
+	t.Parallel()
+
+	validator, err := NewValidator([]string{"token-one", "token-two", "token-three"})
+	if err != nil {
+		t.Fatalf("NewValidator() error = %v", err)
+	}
+
+	tests := []struct {
+		name  string
+		token string
+		want  bool
+	}{
+		{name: "valid token one", token: "token-one", want: true},
+		{name: "valid token two", token: "token-two", want: true},
+		{name: "unknown token", token: "wrong-token", want: false},
+		{name: "empty token", token: "", want: false},
+		{name: "whitespace token", token: "   ", want: false},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			if got := validator.IsValid(tc.token); got != tc.want {
+				t.Fatalf("IsValid() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestNewValidator_EmptyTokenSet(t *testing.T) {
+	t.Parallel()
+
+	if _, err := NewValidator(nil); err == nil {
+		t.Fatal("NewValidator(nil) expected error, got nil")
+	}
+
+	if _, err := NewValidator([]string{"", "   "}); err == nil {
+		t.Fatal("NewValidator(empty tokens) expected error, got nil")
+	}
+}
+
+func TestParseBearerToken(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		header  string
+		want    string
+		wantErr bool
+	}{
+		{name: "valid bearer", header: "Bearer abc123", want: "abc123"},
+		{name: "valid lowercase prefix", header: "bearer abc123", want: "abc123"},
+		{name: "valid uppercase prefix", header: "BEARER abc123", want: "abc123"},
+		{name: "missing header", header: "", wantErr: true},
+		{name: "wrong scheme", header: "Basic abc123", wantErr: true},
+		{name: "missing token", header: "Bearer", wantErr: true},
+		{name: "too many parts", header: "Bearer one two", wantErr: true},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			got, err := ParseBearerToken(tc.header)
+			if tc.wantErr {
+				if err == nil {
+					t.Fatal("ParseBearerToken() expected error, got nil")
+				}
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("ParseBearerToken() error = %v", err)
+			}
+
+			if got != tc.want {
+				t.Fatalf("ParseBearerToken() = %q, want %q", got, tc.want)
+			}
+		})
+	}
+}