Include the link from @RestrictedApi in the diagnostic message.

core/src/main/java/com/google/errorprone/bugpatterns/RestrictedApiChecker.java

@@ -255,6 +255,9 @@ private Description checkRestriction(
     SeverityLevel level = warn ? SeverityLevel.WARNING : SeverityLevel.ERROR;
     Description.Builder description =
         buildDescription(where).setMessage(restriction.explanation()).overrideSeverity(level);
+    if (!restriction.link().isEmpty()) {
+      description.setLinkUrl(restriction.link());
+    }
     return description.build();
   }
 

core/src/test/java/com/google/errorprone/bugpatterns/RestrictedApiCheckerTest.java

@@ -159,6 +159,31 @@ void foo(RestrictedApiMethods m) {
         .doTest();
   }
 
+  @Test
+  public void restrictedCallProhibited_withLink() {
+    helper
+        .addSourceLines(
+            "Testcase.java",
+            """
+            package separate.test;
+
+            import com.google.errorprone.annotations.RestrictedApi;
+
+            class Testcase {
+              void caller() {
+                // BUG: Diagnostic contains: test
+                //    (see http://example.com)
+                restrictedMethod();
+              }
+
+              @RestrictedApi(explanation = "test", link = "http://example.com")
+              void restrictedMethod() {}
+            }
+            """)
+        .expectResult(Result.ERROR)
+        .doTest();
+  }
+
   @Test
   public void restrictedCallProhibited_inherited() {
     helper