Update copyright notice, add SPDX tags (#69)

Author: rfc2822

.idea/codeStyles/Project.xml

@@ -0,0 +1,2 @@
+You can view the list of people who have contributed to the code base in the version control history:
+https://github.com/bitfireAT/dav4jvm/graphs/contributors

.idea/codeStyles/codeStyleConfig.xml

@@ -1,7 +1,11 @@
 /*
+ * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
+ *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * SPDX-License-Identifier: MPL-2.0
  */
 
 package at.bitfire.dav4jvm

.idea/copyright/MPL.xml

@@ -1,7 +1,11 @@
 /*
+ * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
+ *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * SPDX-License-Identifier: MPL-2.0
  */
 
 package at.bitfire.dav4jvm

.idea/copyright/profiles_settings.xml

@@ -1,7 +1,11 @@
 /*
+ * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
+ *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * SPDX-License-Identifier: MPL-2.0
  */
 
 package at.bitfire.dav4jvm

AUTHORS

@@ -1,7 +1,11 @@
 /*
+ * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
+ *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * SPDX-License-Identifier: MPL-2.0
  */
 
 package at.bitfire.dav4jvm

src/main/kotlin/at/bitfire/dav4jvm/BasicDigestAuthHandler.kt

@@ -1,7 +1,11 @@
 /*
+ * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
+ *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * SPDX-License-Identifier: MPL-2.0
  */
 
 package at.bitfire.dav4jvm