[Tech Debt]: MARC BIB records are converted to graph unnecessarily & then discarded

Currently, mod-linked-data processes all newly created MARC bibliographic records in FOLIO from the Kafka topic srs.source_records in order to update the HRID of instance resources in the graph. It converts these MARC records into Resource objects using the marc2LD library. After conversion, it checks if the corresponding instance already exists in the Linked Data graph by matching the inventory instance ID. If no match is found, the newly created Resource is discarded. If a match is found, the existing resource's administrative metadata is updated with the new resource's metadata.

However, the majority of instances do not exist in the Linked Data graph, leading to two main issues:

1. Unnecessary Processing: Many MARC records are converted into Resource objects only to be discarded, consuming unnecessary resources (CPU, Memory).

2. Log Clutter: The log files get filled with unwanted logs from the MARC to Resource conversion process, making debugging and monitoring more difficult.

Proposed Solution:
Refactor the process to first check whether the source of the instance is Linked Data. This can be done by checking for the presence of 999 $l. If 999 $l is not present in the incoming MARC BIB record, then discard the event.