Add Web Portal Export based on Cache Table

[grantfitzsimmons]

For Web Portal exports that require the cache to be modified, they must be created from the cache mechanism used for Darwin Core archives.

Non-Functional Requirements

• The system must use the existing UI mechanism for exporting data (as implemented in [DwC export]: Specify Data Publishing Toolkit #285).
• The system should allow the reuse of mappings established for other data export pipelines (e.g. publishing to GBIF).
• The system should enable users to assign custom terms to the export headings (e.g. not only Darwin Core terms), enabling robust support for any field captions for portal column headings and for searching.

Functional Requirements

• The system must produce a ZIP archive file containing the files necessary for populating the Specify Web Portal.
• Cache Table Utilization: The export process must utilize the flattened cache table architecture. When an export is initiated, the system must build or update the cache table for the selected mapping (e.g., a sanitized {MappingName} table) and draw the export data exclusively from this physical table to improve performance and consistency.
• Creating an export should send the user a notification with a link to download the packaged export.
• This should be something that can be automated using a cronjob, akin to automating the export feed.

The interface must support selecting a 'Core' Schema Mapping, run the mapping to build the flattened cache table, and automatically create a package drawn from that cache that can be imported into the Web Portal. This can be done via a button in the schema mapping interface itself or potentially via a new User Tools option.