[Deprecation] Update URL (elastic#124259)

Replace the URL with the new updated docs URL. Should probably migrate
to ReferenceDocs after 9.1.

Author: prwhelan

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/IndexDeprecationChecker.java

@@ -101,7 +101,7 @@ private DeprecationIssue oldIndicesCheck(
                 return new DeprecationIssue(
                     DeprecationIssue.Level.CRITICAL,
                     "One or more Transforms write to this index with a compatibility version < 9.0",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html"
                         + "#breaking_90_transform_destination_index",
                     Strings.format(
                         "This index was created in version [%s] and requires action before upgrading to 9.0. The following transforms are "
@@ -117,7 +117,7 @@ private DeprecationIssue oldIndicesCheck(
                 return new DeprecationIssue(
                     DeprecationIssue.Level.CRITICAL,
                     "Old index with a compatibility version < 9.0",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-9.0.html",
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html",
                     "This index has version: " + currentCompatibilityVersion.toReleaseVersion(),
                     false,
                     Map.of("reindex_required", true)
@@ -144,7 +144,7 @@ private DeprecationIssue ignoredOldIndicesCheck(
                 return new DeprecationIssue(
                     DeprecationIssue.Level.WARNING,
                     "One or more Transforms write to this old index with a compatibility version < 9.0",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html"
                         + "#breaking_90_transform_destination_index",
                     Strings.format(
                         "This index was created in version [%s] and will be supported as a read-only index in 9.0. The following "
@@ -160,7 +160,7 @@ private DeprecationIssue ignoredOldIndicesCheck(
                 return new DeprecationIssue(
                     DeprecationIssue.Level.WARNING,
                     "Old index with a compatibility version < 9.0 has been ignored",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-9.0.html",
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html",
                     "This read-only index has version: "
                         + currentCompatibilityVersion.toReleaseVersion()
                         + " and will be supported as read-only in 9.0",

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/IndexDeprecationCheckerTests.java

@@ -79,7 +79,7 @@ public void testOldIndicesCheck() {
         DeprecationIssue expected = new DeprecationIssue(
             DeprecationIssue.Level.CRITICAL,
             "Old index with a compatibility version < 9.0",
-            "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-9.0.html",
+            "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html",
             "This index has version: " + OLD_VERSION.toReleaseVersion(),
             false,
             singletonMap("reindex_required", true)
@@ -103,8 +103,7 @@ public void testOldTransformIndicesCheck() {
         var expected = new DeprecationIssue(
             DeprecationIssue.Level.CRITICAL,
             "One or more Transforms write to this index with a compatibility version < 9.0",
-            "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
-                + "#breaking_90_transform_destination_index",
+            "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html#breaking_90_transform_destination_index",
             "This index was created in version ["
                 + OLD_VERSION.toReleaseVersion()
                 + "] and requires action before upgrading to 9.0. "
@@ -130,8 +129,7 @@ public void testOldIndicesCheckWithMultipleTransforms() {
         var expected = new DeprecationIssue(
             DeprecationIssue.Level.CRITICAL,
             "One or more Transforms write to this index with a compatibility version < 9.0",
-            "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
-                + "#breaking_90_transform_destination_index",
+            "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html#breaking_90_transform_destination_index",
             "This index was created in version ["
                 + OLD_VERSION.toReleaseVersion()
                 + "] and requires action before upgrading to 9.0. "
@@ -161,7 +159,7 @@ public void testMultipleOldIndicesCheckWithTransforms() {
                 new DeprecationIssue(
                     DeprecationIssue.Level.CRITICAL,
                     "One or more Transforms write to this index with a compatibility version < 9.0",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html"
                         + "#breaking_90_transform_destination_index",
                     "This index was created in version ["
                         + OLD_VERSION.toReleaseVersion()
@@ -177,7 +175,7 @@ public void testMultipleOldIndicesCheckWithTransforms() {
                 new DeprecationIssue(
                     DeprecationIssue.Level.CRITICAL,
                     "One or more Transforms write to this index with a compatibility version < 9.0",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html"
                         + "#breaking_90_transform_destination_index",
                     "This index was created in version ["
                         + OLD_VERSION.toReleaseVersion()
@@ -284,7 +282,7 @@ public void testOldIndicesIgnoredWarningCheck() {
         DeprecationIssue expected = new DeprecationIssue(
             DeprecationIssue.Level.WARNING,
             "Old index with a compatibility version < 9.0 has been ignored",
-            "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-9.0.html",
+            "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html",
             "This read-only index has version: " + OLD_VERSION.toReleaseVersion() + " and will be supported as read-only in 9.0",
             false,
             singletonMap("reindex_required", true)
@@ -335,8 +333,7 @@ public void testOldTransformIndicesIgnoredCheck() {
         var expected = new DeprecationIssue(
             DeprecationIssue.Level.WARNING,
             "One or more Transforms write to this old index with a compatibility version < 9.0",
-            "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
-                + "#breaking_90_transform_destination_index",
+            "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html#breaking_90_transform_destination_index",
             "This index was created in version ["
                 + OLD_VERSION.toReleaseVersion()
                 + "] and will be supported as a read-only index in 9.0. "
@@ -362,8 +359,7 @@ public void testOldIndicesIgnoredCheckWithMultipleTransforms() {
         var expected = new DeprecationIssue(
             DeprecationIssue.Level.WARNING,
             "One or more Transforms write to this old index with a compatibility version < 9.0",
-            "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
-                + "#breaking_90_transform_destination_index",
+            "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html#breaking_90_transform_destination_index",
             "This index was created in version ["
                 + OLD_VERSION.toReleaseVersion()
                 + "] and will be supported as a read-only index in 9.0. "
@@ -393,7 +389,7 @@ public void testMultipleOldIndicesIgnoredCheckWithTransforms() {
                 new DeprecationIssue(
                     DeprecationIssue.Level.WARNING,
                     "One or more Transforms write to this old index with a compatibility version < 9.0",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html"
                         + "#breaking_90_transform_destination_index",
                     "This index was created in version ["
                         + OLD_VERSION.toReleaseVersion()
@@ -409,7 +405,7 @@ public void testMultipleOldIndicesIgnoredCheckWithTransforms() {
                 new DeprecationIssue(
                     DeprecationIssue.Level.WARNING,
                     "One or more Transforms write to this old index with a compatibility version < 9.0",
-                    "https://www.elastic.co/guide/en/elasticsearch/reference/master/migrating-9.0.html"
+                    "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html"
                         + "#breaking_90_transform_destination_index",
                     "This index was created in version ["
                         + OLD_VERSION.toReleaseVersion()