Deprecate oauth/tokens endpoint

This PR implements "M1" of [this
document](https://docs.google.com/document/d/1Xi5MRk8WdBWFC3N_eSmVcrLhk3yu5nJ9x_wC0ec6kVQ/), see #10537.

build.gradle

@@ -373,6 +373,7 @@ project(':iceberg-core') {
     testImplementation libs.esotericsoftware.kryo
     testImplementation libs.guava.testlib
     testImplementation libs.awaitility
+    testRuntimeOnly libs.logback.classic
   }
 }
 

core/src/main/java/org/apache/iceberg/rest/RESTSessionCatalog.java

@@ -183,6 +183,17 @@ public void initialize(String name, Map<String, String> unresolved) {
     String credential = props.get(OAuth2Properties.CREDENTIAL);
     String scope = props.getOrDefault(OAuth2Properties.SCOPE, OAuth2Properties.CATALOG_SCOPE);
     Map<String, String> optionalOAuthParams = OAuth2Util.buildOptionalParam(props);
+    if (!props.containsKey(OAuth2Properties.OAUTH2_SERVER_URI)) {
+      LOG.warn(
+          "Iceberg REST client is missing the OAuth2 server URI configuration and defaults to {}{}. "
+              + "This automatic fallback will be removed in a future Iceberg release."
+              + "It is recommended to configure the OAuth2 endpoint using the '{}' property to be prepared. "
+              + "This warning will disappear if the OAuth2 endpoint is explicitly configured. "
+              + "See https://github.com/apache/iceberg/issues/10537",
+          props.get(CatalogProperties.URI),
+          ResourcePaths.tokens(),
+          OAuth2Properties.OAUTH2_SERVER_URI);
+    }
     String oauth2ServerUri =
         props.getOrDefault(OAuth2Properties.OAUTH2_SERVER_URI, ResourcePaths.tokens());
     try (RESTClient initClient = clientBuilder.apply(props)) {

core/src/test/resources/logback-test.xml

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!--
+
+    Licensed to the Apache Software Foundation (ASF) under one
+    or more contributor license agreements.  See the NOTICE file
+    distributed with this work for additional information
+    regarding copyright ownership.  The ASF licenses this file
+    to you under the Apache License, Version 2.0 (the
+    "License"); you may not use this file except in compliance
+    with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing,
+    software distributed under the License is distributed on an
+    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+    KIND, either express or implied.  See the License for the
+    specific language governing permissions and limitations
+    under the License.
+
+-->
+<configuration debug="true">
+  <contextListener class="ch.qos.logback.classic.jul.LevelChangePropagator"/>
+  <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%date{ISO8601} [%thread] %-5level %logger{36} - %msg%n</pattern>
+    </encoder>
+  </appender>
+  <root level="${test.log.level:-WARN}">
+    <appender-ref ref="console"/>
+  </root>
+</configuration>

gradle/libs.versions.toml

@@ -63,6 +63,7 @@ jetty = "9.4.54.v20240208"
 junit = "5.10.1"
 kafka = "3.7.0"
 kryo-shaded = "4.0.3"
+logback = "1.3.14"
 microprofile-openapi-api = "3.1.1"
 mockito = "4.11.0"
 mockserver = "5.15.0"
@@ -201,6 +202,7 @@ junit-jupiter = { module = "org.junit.jupiter:junit-jupiter", version.ref = "jun
 junit-jupiter-engine = { module = "org.junit.jupiter:junit-jupiter-engine", version.ref = "junit" }
 junit-vintage-engine = { module = "org.junit.vintage:junit-vintage-engine", version.ref = "junit" }
 kryo-shaded = { module = "com.esotericsoftware:kryo-shaded", version.ref = "kryo-shaded" }
+logback-classic = { module = "ch.qos.logback:logback-classic", version.ref = "logback" }
 mockito-core = { module = "org.mockito:mockito-core", version.ref = "mockito" }
 mockito-inline = { module = "org.mockito:mockito-inline", version.ref = "mockito" }
 mockito-junit-jupiter = { module = "org.mockito:mockito-junit-jupiter", version.ref = "mockito" }

open-api/rest-catalog-open-api.yaml

@@ -134,9 +134,20 @@ paths:
     post:
       tags:
         - OAuth2 API
-      summary: Get a token using an OAuth2 flow
+      summary: Get a token using an OAuth2 flow (DEPRECATED for REMOVAL)
+      deprecated: true
       operationId: getToken
       description:
+        The `oauth/tokens` endpoint is **DEPRECATED for REMOVAL**. It is not recommended to _not_
+        implement this endpoint, unless you are fully aware of the potential security implications.
+        All clients are encouraged to explicitly set the configuration property `oauth2-server-uri`
+        to the correct OAuth endpoint.
+        See [Security improvements in the Iceberg REST specification](https://github.com/apache/iceberg/issues/10537)
+
+
+        Old description follows
+
+
         Exchange credentials for a token using the OAuth2 client credentials flow or token exchange.