enable bwc tests and switch transport serialization version to 6.6.0 for CAS features

Relates to #36148

Author: bleskes

build.gradle

@@ -163,8 +163,8 @@ task verifyVersions {
  * the enabled state of every bwc task. It should be set back to true
  * after the backport of the backcompat code is complete.
  */
-final boolean bwc_tests_enabled = false
-final String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/36555" /* place a PR link here when committing bwc changes */
+final boolean bwc_tests_enabled = true
+final String bwc_tests_disabled_issue = "" /* place a PR link here when committing bwc changes */
 if (bwc_tests_enabled == false) {
   if (bwc_tests_disabled_issue.isEmpty()) {
     throw new GradleException("bwc_tests_disabled_issue must be set when bwc_tests_enabled == false")

server/src/main/java/org/elasticsearch/action/delete/DeleteRequest.java

@@ -282,7 +282,7 @@ public void readFrom(StreamInput in) throws IOException {
         }
         version = in.readLong();
         versionType = VersionType.fromValue(in.readByte());
-        if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (in.getVersion().onOrAfter(Version.V_6_6_0)) {
             ifSeqNo = in.readZLong();
             ifPrimaryTerm = in.readVLong();
         } else {
@@ -302,7 +302,7 @@ public void writeTo(StreamOutput out) throws IOException {
         }
         out.writeLong(version);
         out.writeByte(versionType.getValue());
-        if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_6_6_0)) {
             out.writeZLong(ifSeqNo);
             out.writeVLong(ifPrimaryTerm);
         } else if (ifSeqNo != SequenceNumbers.UNASSIGNED_SEQ_NO || ifPrimaryTerm != 0) {

server/src/main/java/org/elasticsearch/action/index/IndexRequest.java

@@ -616,7 +616,7 @@ public void readFrom(StreamInput in) throws IOException {
         } else {
             contentType = null;
         }
-        if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (in.getVersion().onOrAfter(Version.V_6_6_0)) {
             ifSeqNo = in.readZLong();
             ifPrimaryTerm = in.readVLong();
         } else {
@@ -654,7 +654,7 @@ public void writeTo(StreamOutput out) throws IOException {
         } else {
             out.writeBoolean(false);
         }
-        if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_6_6_0)) {
             out.writeZLong(ifSeqNo);
             out.writeVLong(ifPrimaryTerm);
         } else if (ifSeqNo != SequenceNumbers.UNASSIGNED_SEQ_NO || ifPrimaryTerm != 0) {

server/src/main/java/org/elasticsearch/index/get/GetResult.java

@@ -384,7 +384,7 @@ public void readFrom(StreamInput in) throws IOException {
         index = in.readString();
         type = in.readOptionalString();
         id = in.readString();
-        if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (in.getVersion().onOrAfter(Version.V_6_6_0)) {
             seqNo = in.readZLong();
             primaryTerm = in.readVLong();
         } else {
@@ -416,7 +416,7 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeString(index);
         out.writeOptionalString(type);
         out.writeString(id);
-        if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_6_6_0)) {
             out.writeZLong(seqNo);
             out.writeVLong(primaryTerm);
         }