Add markers to data products

[timcanham]

F´ Version	v3.4.3
Affected Component	n/a

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Feature Description

Add a marker token between records in a data product container.

Rationale

If a partial or corrupted data product is received on the ground, markers can provide an opportunity to extract as many records from the data product container as possible. (Suggested in a meeting)

[LeStarch]

@bocchino do you agree with this change? If so, we will approved for the backlog.

[bocchino]

Yes, but it looks like a duplicate of nasa/fpp#584. Can we close this issue in favor of that one?