Feat(receiver): Add endpoint for callback

src/main/java/de/bund/digitalservice/a2j/config/SecurityConfig.java

@@ -13,7 +13,8 @@ public class SecurityConfig {
 
   @Bean
   public SecurityFilterChain springSecurityWebFilterChain(HttpSecurity http) throws Exception {
-    return http.csrf(csrf -> csrf.ignoringRequestMatchers("/api/sender/submit"))
+    return http.csrf(
+            csrf -> csrf.ignoringRequestMatchers("/api/sender/submit", "/callbacks/fit-connect"))
         .authorizeHttpRequests(
             requests ->
                 requests
@@ -23,6 +24,8 @@ public SecurityFilterChain springSecurityWebFilterChain(HttpSecurity http) throw
                     .permitAll()
                     .requestMatchers("/api/sender/**")
                     .permitAll()
+                    .requestMatchers("/callbacks/fit-connect")
+                    .permitAll()
                     .anyRequest()
                     .denyAll())
         .build();

src/main/java/de/bund/digitalservice/a2j/controller/ReceiverController.java

@@ -0,0 +1,16 @@
+package de.bund.digitalservice.a2j.controller;
+
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class ReceiverController {
+
+  public ReceiverController() {}
+  ;
+
+  @PostMapping("callbacks/fit-connect")
+  public void newSubmission() {
+    System.out.println("new Submission via callback!");
+  }
+}

src/test/java/de/bund/digitalservice/a2j/integration/ReceiverIntegrationTest.java

@@ -0,0 +1,24 @@
+package de.bund.digitalservice.a2j.integration;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import org.junit.jupiter.api.Tag;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.test.web.servlet.MockMvc;
+
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@AutoConfigureMockMvc
+@Tag("integration")
+public class ReceiverIntegrationTest {
+  @Autowired private MockMvc mockMvc;
+
+  @Test
+  void shouldExposeSecurityTxt() throws Exception {
+    mockMvc.perform(post("/callbacks/fit-connect")).andExpect(status().isOk());
+  }
+}