Add rest-client-test module: @RestClientTest on Boot 4.1, Jackson 3 by default, and the RestClient-vs-RestTemplate root-URI matching trap (post #49)

rest-client-test/src/main/java/com/ankurm/restclienttest/EmployeeAuditLogger.java

@@ -0,0 +1,12 @@
+package com.ankurm.restclienttest;
+
+/**
+ * A collaborator {@code EmployeeClient} depends on but that has nothing to do with REST clients
+ * itself. {@code @RestClientTest}'s minimal context never creates a bean for this on its own -
+ * it exists specifically so the test class can demonstrate replacing it with
+ * {@code @MockitoBean}, now that {@code @MockBean} is gone in Spring Boot 4.
+ */
+public interface EmployeeAuditLogger {
+
+    void logFetch(Integer employeeId);
+}