Consistent method to store and fetch metadata associated with a message

Have a consistent method to store and retrieve metadata that follows the message lifecycle. It should allow storing objects and variables in a simple way regardless of message type (HL7, SDA, FHIR, etc). It should be accessible across DTLs and BPs (and regardless of DTL context).

Example syntax could be:

MessageMetaData.put("key", "value to store")
MessageMetaData.get("key")

Simple example: during HL7 processing store activeEncounter which maybe used in downstream FHIR DTLs.

Set eventType = pHL7.GetValueAt("MSH:9.2")
Set dischargeDate = pHL7.GetValueAt("PV1:45")
if ((dischargeDate '= "") || (eventType = "A11") || (eventType = "A38")) {
    Set tActiveEncounter = 0
} else {
    Set tActiveEncounter = 1
}
/// Store variable into metadata
MessageMetaData.put("activeEncounter", tActiveEncounter)

Within a DTL allow for ease of access:

If (MessageMetaData.get("activeEncounter")) {
/// active encounter logic
}

While there are ways of either adding metadata to the message itself or customising IRIS with persisitent classes it would be great to have a standard method available that provides the following benefits:

1. Safe by design, using persistent classes require manual keying with the message/session.

2. Avoids polluting the message payload by not adding metadata to the message itself.

3. Built in lifecycle management that tracks the message lifecycle.