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.api/build.gradle.kts

@@ -1,6 +1,6 @@
 description = "OpenCloudCal : API"
 
 dependencies {
-    implementation("de.srsoftware:tools.util:1.2.3")
+    implementation("de.srsoftware:tools.util:1.3.0")
     implementation("org.json:json:20240303")
 }

de.srsoftware.cal.api/src/main/java/de/srsoftware/cal/api/Appointment.java

@@ -37,6 +37,14 @@ public interface Appointment {
 	 */
 	Optional<LocalDateTime> end();
 
+
+	/**
+	 * represent this event as ical entry
+	 * @return the ical string
+	 */
+	String ical();
+
+
 	/**
 	 * ID of the appointment – unique within this system
 	 * @return the appointment`s id
@@ -49,6 +57,12 @@ public interface Appointment {
 	 */
 	JSONObject json();
 
+	/**
+	 * set of Links that point to related information
+	 * @return set of links
+	 */
+	Set<Link> links();
+
 	/**
 	 * descriptive text of the location, e.g. address
 	 * @return location text
@@ -74,10 +88,4 @@ public interface Appointment {
 	 * @return the title
 	 */
 	String title();
-
-	/**
-	 * set of Links that point to related information
-	 * @return set of links
-	 */
-	Set<Link> urls();
 }