fix(protocol): add getActivatedElementInstanceKeys to interface

This method needs to be part of the interface in order for the ElasticSearchIT to generate a record containing this field, and verifying exporting works as expected.

(cherry picked from commit c3acb60)

protocol-impl/src/main/java/io/camunda/zeebe/protocol/impl/record/value/processinstance/ProcessInstanceModificationRecord.java

@@ -80,6 +80,13 @@ public List<ProcessInstanceModificationActivateInstructionValue> getActivateInst
         .toList();
   }
 
+  @Override
+  public Set<Long> getActivatedElementInstanceKeys() {
+    return activatedElementInstanceKeys.stream()
+        .map(LongValue::getValue)
+        .collect(Collectors.toSet());
+  }
+
   /** Returns true if this record has terminate instructions, otherwise false. */
   @JsonIgnore
   public boolean hasTerminateInstructions() {
@@ -104,12 +111,6 @@ public ProcessInstanceModificationRecord addActivateInstruction(
     return this;
   }
 
-  public Set<Long> getActivatedElementInstanceKeys() {
-    return activatedElementInstanceKeys.stream()
-        .map(LongValue::getValue)
-        .collect(Collectors.toSet());
-  }
-
   public ProcessInstanceModificationRecord addActivatedElementInstanceKey(final long key) {
     activatedElementInstanceKeys.add().setValue(key);
     return this;

protocol/src/main/java/io/camunda/zeebe/protocol/record/value/ProcessInstanceModificationRecordValue.java

@@ -19,6 +19,7 @@
 import io.camunda.zeebe.protocol.record.RecordValue;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import org.immutables.value.Value;
 
 @Value.Immutable
@@ -32,6 +33,8 @@ public interface ProcessInstanceModificationRecordValue
   /** Returns a list of activate instructions (if available), or an empty list. */
   List<ProcessInstanceModificationActivateInstructionValue> getActivateInstructions();
 
+  Set<Long> getActivatedElementInstanceKeys();
+
   @Value.Immutable
   @ImmutableProtocol(
       builder = ImmutableProcessInstanceModificationTerminateInstructionValue.Builder.class)