Added version display

- Added error route handling

src/main/java/de/w665/sharepulse/rest/ErrorRestController.java

@@ -0,0 +1,19 @@
+package de.w665.sharepulse.rest;
+
+import org.springframework.boot.web.servlet.error.ErrorController;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * This class is used to redirect the user to the home page if an endpoint is not found.
+ */
+@RestController
+public class ErrorRestController implements ErrorController {
+    @RequestMapping("/error")
+    public String handleError() {
+        return "<script>" +
+                    "console.log('Page not found. Redirecting to /home...');" +
+                    "window.location.href = window.location.origin + '/home';" +
+                "</script>";
+    }
+}

src/main/java/de/w665/sharepulse/rest/mappings/Version.java

@@ -0,0 +1,37 @@
+package de.w665.sharepulse.rest.mappings;
+
+import com.rethinkdb.net.Response;
+import de.w665.sharepulse.rest.ApiRestController;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.jar.Attributes;
+import java.util.jar.Manifest;
+
+@RestController
+public class Version extends ApiRestController {
+
+    private final ResourceLoader resourceLoader;
+
+    @Autowired
+    public Version(ResourceLoader resourceLoader) {
+        this.resourceLoader = resourceLoader;
+    }
+
+    @GetMapping("/version")
+    public ResponseEntity<Object> getVersion() throws Exception {
+        Resource resource = resourceLoader.getResource("classpath:META-INF/MANIFEST.MF");
+        Manifest manifest = new Manifest(resource.getInputStream());
+        Attributes attr = manifest.getMainAttributes();
+        String version = attr.getValue("Application-Version");
+        String response = version != null ? version : "Version is only available in production builds";
+        return new ResponseEntity<>(response, HttpStatus.OK);
+    }
+}