fix(rerankers): send the Nvidia reranker base URL as "baseURL"

src/main/java/io/weaviate/client6/v1/api/collections/rerankers/NvidiaReranker.java

@@ -9,7 +9,14 @@
 
 public record NvidiaReranker(
     @SerializedName("model") String model,
-    @SerializedName("baseUrl") String baseUrl) implements Reranker {
+    /**
+     * The module reads this as {@code baseURL}: {@code reranker-nvidia} looks the
+     * key up verbatim, so a {@code baseUrl} spelling is stored in the schema and
+     * then ignored, and reranking silently goes to the default endpoint. The
+     * {@code alternate} keeps configs written by older versions of this client
+     * readable; Gson only ever writes {@code value}.
+     */
+    @SerializedName(value = "baseURL", alternate = { "baseUrl" }) String baseUrl) implements Reranker {
 
   @Override
   public Kind _kind() {

src/test/java/io/weaviate/client6/v1/api/collections/rerankers/NvidiaRerankerTest.java

@@ -0,0 +1,37 @@
+package io.weaviate.client6.v1.api.collections.rerankers;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+import io.weaviate.client6.v1.api.collections.Reranker;
+import io.weaviate.client6.v1.internal.json.JSON;
+
+public class NvidiaRerankerTest {
+
+  /**
+   * Collections created by earlier versions of this client have the base URL
+   * stored under the "baseUrl" key the module never read. Those configs still
+   * have to deserialize, otherwise upgrading turns a wrong value into a missing
+   * one.
+   */
+  @Test
+  public void test_readsLegacyBaseUrlKey() {
+    var legacy = """
+        {"reranker-nvidia": {"baseUrl": "https://legacy.example.com"}}
+        """;
+
+    var reranker = JSON.deserialize(legacy, Reranker.class);
+
+    Assertions.assertThat(reranker)
+        .asInstanceOf(org.assertj.core.api.InstanceOfAssertFactories.type(NvidiaReranker.class))
+        .returns("https://legacy.example.com", NvidiaReranker::baseUrl);
+  }
+
+  /** ...but writing always uses the key the module actually reads. */
+  @Test
+  public void test_writesCanonicalBaseUrlKey() {
+    var json = JSON.serialize(Reranker.nvidia(r -> r.baseUrl("https://example.com")));
+
+    Assertions.assertThat(json).contains("\"baseURL\"").doesNotContain("\"baseUrl\"");
+  }
+}

src/test/java/io/weaviate/client6/v1/internal/json/JSONTest.java

@@ -1476,6 +1476,23 @@ public static Object[][] testCases() {
                 }
                   """,
         },
+        // reranker-nvidia reads "baseURL" like every other module. It had no test
+        // row, which is how it kept sending "baseUrl" -- stored in the schema and
+        // then ignored, so reranking silently used the default endpoint.
+        {
+            Reranker.class,
+            Reranker.nvidia(rerank -> rerank
+                .baseUrl("example.com")
+                .model("nvidia/rerank-qa-mistral-4b")),
+            """
+                {
+                  "reranker-nvidia": {
+                    "baseURL": "example.com",
+                    "model": "nvidia/rerank-qa-mistral-4b"
+                  }
+                }
+                  """,
+        },
 
         // BatchReference.CustomTypeAdapterFactory
         {