[DwC export]: Build flattened cache tables for core and extension mappings

[grantfitzsimmons]

Goal

When an export package is run, build a flattened cache table for the core mapping and one per extension, using a consistent naming convention.

This will be what the DwC-A is built from.

Background

Cache tables allow institutions to post-process exported data. Extension tables must be named predictably and include occurrenceID to facilitate joins.

Acceptance Criteria

• Core cache table is named {MappingName} (sanitized).
• Extension cache tables are named {MappingName}_ext{N}_{ExtensionName} (e.g., dwc_fish_ext1_audiovisual).
• All data from the source query is inserted into the cache table.
• Rows whose source records no longer exist are deleted from the cache.
• Each cache table includes occurrenceID to enable joins between core and extensions.