Added InvalidSettingsException

Added unchecked InvalidSettingsException as indicator for problems with the user config
Added AbstractInvalidSetting as interface for identifiers/handlers for such problems
Added InvalidSetting as enum implementation of AbstractInvalidSetting

src/main/java/org/cryptomator/common/settings/AbstractInvalidSetting.java

@@ -0,0 +1,23 @@
+package org.cryptomator.common.settings;
+
+import java.net.URI;
+
+public interface AbstractInvalidSetting {
+
+	/**
+	 * Returns the corresponding issue URI of this setting.<br>
+	 * The issue URI usually resolves to a page on the
+	 * <a href="https://github.com/cryptomator/cryptomator/issues">Cryptomator Bugtracker.</a>
+	 *
+	 * @return the issue URI or {@code null} if none is provided.
+	 */
+	URI getIssueURI();
+
+	/**
+	 * Returns a (preferably localized) message, that helps the user understand the
+	 * issue in their configuration and how to fix it.
+	 *
+	 * @return the non-null description of the issue.
+	 */
+	String getMessage();
+}

src/main/java/org/cryptomator/common/settings/InvalidSetting.java

@@ -0,0 +1,43 @@
+package org.cryptomator.common.settings;
+
+import java.net.URI;
+import java.util.Objects;
+import java.util.ResourceBundle;
+
+public enum InvalidSetting implements AbstractInvalidSetting {
+
+	;
+
+	private final static String DEFAULT_TRACKER = "https://github.com/cryptomator/cryptomator/issues/";
+	private final static ResourceBundle BUNDLE = ResourceBundle.getBundle("i18n.strings");
+	private final static String UNKNOWN_KEY_FORMAT = "<Unknown key: %s>";
+
+	private final URI issue;
+	private final String resourceKey;
+
+	InvalidSetting(URI issue, String resourceKey) {
+		this.issue = issue;
+		this.resourceKey = Objects.requireNonNull(resourceKey);
+	}
+
+	InvalidSetting(int issueId, String resourceKey) {
+		this(onDefaultTracker(issueId), Objects.requireNonNull(resourceKey));
+	}
+
+	@Override
+	public URI getIssueURI() {
+		return this.issue;
+	}
+
+	@Override
+	public String getMessage() {
+		if (!BUNDLE.containsKey(this.resourceKey)) {
+			return UNKNOWN_KEY_FORMAT.formatted(this.resourceKey);
+		}
+		return BUNDLE.getString(this.resourceKey);
+	}
+
+	private static URI onDefaultTracker(int id) {
+		return URI.create(DEFAULT_TRACKER + id);
+	}
+}

src/main/java/org/cryptomator/common/settings/InvalidSettingsException.java

@@ -0,0 +1,42 @@
+package org.cryptomator.common.settings;
+
+
+public class InvalidSettingsException extends RuntimeException {
+
+	private final AbstractInvalidSetting reason;
+	private final String additionalMessage;
+
+	public InvalidSettingsException(AbstractInvalidSetting reason) {
+		this(reason, null, null);
+	}
+
+	public InvalidSettingsException(AbstractInvalidSetting reason, String additionalMessage) {
+		this(reason, additionalMessage, null);
+	}
+
+	public InvalidSettingsException(AbstractInvalidSetting reason, Throwable cause) {
+		this(reason, null, cause);
+	}
+
+	public InvalidSettingsException(AbstractInvalidSetting reason, String additionalMessage, Throwable cause) {
+		super(composeMessage(reason, additionalMessage), cause);
+		this.reason = reason;
+		this.additionalMessage = additionalMessage;
+	}
+
+	public AbstractInvalidSetting getReason() {
+		return this.reason;
+	}
+
+	public String getAdditionalMessage() {
+		return this.additionalMessage;
+	}
+
+	private static String composeMessage(AbstractInvalidSetting reason, String additionalMessage) {
+		if (additionalMessage == null) {
+			return reason.getMessage();
+		}
+		return reason.getMessage() + "\n" //
+				+ "Additionally: " + additionalMessage;
+	}
+}