Honor suppress from discovery flag in OAI-PMH

Overview:
Suppression status or suppress from discovery flag indicates that the record is "suppressed" and should not be displayed in a discovery system. This element provides a means of excluding suppressed records from the total title count.
Suppress from discovery flag exists on all record levels in inventory: instance, holding and item. It is stored in fields with name “discoverySuppress” and can have one of two values: true or false.
“true” means the record is suppressed and “false” means the opposite.
For SRS there is only one level - instance record - and one flag accordingly. It isn’t stored inside the MARC record itself, but in additional properties (metadata related to MARC).

What needs to be done
OAI-PMH should consider suppression flag on all levels of existence: instance, holding and item. Since individual bib records, holdings or item records can be suppressed separately, flag values conflicts might take place in the records hierarchy. Such conflicts should be resolved using the next rule:

• If a precedence record is suppressed, then all successive records are suppressed as well.
• For the successive record, the flag is considered only if a precedence record isn’t suppressed.

Discovery suppression might be processed in two ways for OAI-PMH:

• Suppressed record is ignored (skipped) by OAI-PMH and not transferred to Discovery Layer
• All records are available for retrieval via OAI-PMH, suppression flag value is included into each record