Set up operation_key as nullable

for support B2B implementations

Author: nuzil

app/code/Magento/AsynchronousOperations/etc/db_schema.xml

@@ -34,7 +34,7 @@
     <table name="magento_operation" resource="default" engine="innodb" comment="Operation entity">
         <column xsi:type="int" name="id" padding="10" unsigned="true" nullable="false" identity="true"
                 comment="Operation ID"/>
-        <column xsi:type="int" name="operation_key" padding="10" unsigned="true" nullable="false"
+        <column xsi:type="int" name="operation_key" padding="10" unsigned="true" nullable="true"
                 comment="Operation Key"/>
         <column xsi:type="varbinary" name="bulk_uuid" nullable="true" length="39" comment="Related Bulk UUID"/>
         <column xsi:type="varchar" name="topic_name" nullable="true" length="255"