fix(ProtoBuf): add LicenseExpression.bom_ref

schema/bom-1.6.proto

@@ -373,6 +373,8 @@ message LicenseChoice {
   }
   // This field must only be used when "expression" is chosen as the License object has its own acknowledgement.
   optional LicenseAcknowledgementEnumeration acknowledgement = 3;
+  // This field must only be used when "expression" is chosen as the License object has its own bom_ref.
+  optional string bom_ref = 4;
 }
 
 // Specifies the details and attributes related to a software license. It can either include a valid SPDX license identifier or a named license, along with additional properties such as license acknowledgment, comprehensive commercial licensing information, and the full text of the license.

tools/src/test/resources/1.6/valid-license-expression-1.6.textproto

@@ -13,5 +13,6 @@ components {
   licenses {
     expression: "EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0"
     acknowledgement: LICENSE_ACKNOWLEDGEMENT_ENUMERATION_DECLARED
+    bom_ref: "my-license"
   }
 }