Added error codes to error screen (#1741)

Added error codes based on a translation of GeneratedErrorCode.kt (Cryptomator Android) into Java:

Source of GeneratedErrorCode.kt: https://github.com/cryptomator/android/blob/3ae90ab521a4aa69f394c0490f27e9db6106ce0e/presentation/src/main/java/org/cryptomator/presentation/logging/GeneratedErrorCode.kt

Co-authored-by: Sebastian Stenzel <sebastian.stenzel@gmail.com>

src/test/java/org/cryptomator/common/ErrorCodeTest.java

@@ -0,0 +1,130 @@
+package org.cryptomator.common;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+public class ErrorCodeTest {
+
+	private static ErrorCode codeCaughtFrom(RunnableThrowingException<RuntimeException> runnable) {
+		try {
+			runnable.run();
+			throw new IllegalStateException("should not reach this point");
+		} catch (RuntimeException e) {
+			return ErrorCode.of(e);
+		}
+	}
+
+	@Test
+	@DisplayName("same exception leads to same error code")
+	public void testDifferentErrorCodes() {
+		var code1 = codeCaughtFrom(this::throwNpe);
+		var code2 = codeCaughtFrom(this::throwNpe);
+
+		Assertions.assertEquals(code1.toString(), code2.toString());
+	}
+
+	private void throwNpe() {
+		throwException(new NullPointerException());
+	}
+
+	private void throwException(RuntimeException e) throws RuntimeException {
+		throw e;
+	}
+
+	@DisplayName("when different cause but same root cause")
+	@Nested
+	public class SameRootCauseDifferentCause {
+
+		private final ErrorCode code1 = codeCaughtFrom(this::foo);
+		private final ErrorCode code2 = codeCaughtFrom(this::bar);
+
+		private void foo() throws IllegalArgumentException {
+			try {
+				throwNpe();
+			} catch (NullPointerException e) {
+				throw new IllegalArgumentException(e);
+			}
+		}
+
+		private void bar() throws IllegalStateException {
+			try {
+				throwNpe();
+			} catch (NullPointerException e) {
+				throw new IllegalStateException(e);
+			}
+		}
+
+		@Test
+		@DisplayName("error codes are different")
+		public void testDifferentCodes() {
+			Assertions.assertNotEquals(code1.toString(), code2.toString());
+		}
+
+		@Test
+		@DisplayName("throwableCodes are different")
+		public void testDifferentThrowableCodes() {
+			Assertions.assertNotEquals(code1.throwableCode(), code2.throwableCode());
+		}
+
+		@Test
+		@DisplayName("rootCauseCodes are equal")
+		public void testSameRootCauseCodes() {
+			Assertions.assertEquals(code1.rootCauseCode(), code2.rootCauseCode());
+		}
+
+		@Test
+		@DisplayName("methodCode are equal")
+		public void testSameMethodCodes() {
+			Assertions.assertEquals(code1.methodCode(), code2.methodCode());
+		}
+
+	}
+
+	@DisplayName("when same cause but different call stack")
+	@Nested
+	public class SameCauseDifferentCallStack {
+
+		private final ErrorCode code1 = codeCaughtFrom(this::foo);
+		private final ErrorCode code2 = codeCaughtFrom(this::bar);
+
+		private void foo() throws NullPointerException {
+			try {
+				throwNpe();
+			} catch (NullPointerException e) {
+				throw new IllegalArgumentException(e);
+			}
+		}
+
+		private void bar() throws NullPointerException {
+			foo();
+		}
+
+		@Test
+		@DisplayName("error codes are different")
+		public void testDifferentCodes() {
+			Assertions.assertNotEquals(code1.toString(), code2.toString());
+		}
+
+		@Test
+		@DisplayName("throwableCodes are different")
+		public void testDifferentThrowableCodes() {
+			Assertions.assertNotEquals(code1.throwableCode(), code2.throwableCode());
+		}
+
+		@Test
+		@DisplayName("rootCauseCodes are equal")
+		public void testSameRootCauseCodes() {
+			Assertions.assertEquals(code1.rootCauseCode(), code2.rootCauseCode());
+		}
+
+		@Test
+		@DisplayName("methodCode are equal")
+		public void testSameMethodCodes() {
+			Assertions.assertEquals(code1.methodCode(), code2.methodCode());
+		}
+
+	}
+
+}