overhauled API:

- wrote openapi schema
- re-implemented api endpoint following openapi schema
- intensified and improved working with Result objects

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

de.srsoftware.cal.db/src/main/java/de/srsoftware/cal/db/NotFound.java

@@ -0,0 +1,22 @@
+/* © SRSoftware 2024 */
+package de.srsoftware.cal.db;
+
+import de.srsoftware.tools.Error;
+import java.util.Collection;
+import java.util.Map;
+
+public class NotFound<None> extends Error<None> {
+	public NotFound(String message, Map<String, Object> data, Collection<Exception> exceptions) {
+		super(message, data, exceptions);
+	}
+
+	public static <T> NotFound<T> of(String message, Object... fills) {
+		return new NotFound<>(message.formatted(fills), null, null);
+	}
+
+
+	@Override
+	public <NewType> NotFound<NewType> transform() {
+		return new NotFound<>(message(), data(), exceptions());
+	}
+}