Description
add businessSystem identifier to the structured data from configurable value

Use case or motivation behind the feature request
current implementation identifies only the technical component that is streaming records. multiple components may be used within a businessSystem depending on organizational needs to group them. therefore a grouping mechanism is needed.

Related issues
teragrep/jla_01#54

Additional context
please add configuration so that it can be defined as constant for all records

log4j.appender.RELPAPPENDER.businessSystemId=x

that will result to structured data that is being added to the records as

[businessSystem@48577 systemId="x"]