DISA Excel Export column ordering is not consistent with the DISA provided STIGTemplate spreadsheet

[skykam87]

A review of the column ordering on several DISA provided STIGTemplate spreadsheets indicates a consistent column ordering as follows:

'IA Control', 'CCI', 'SRGID', 'STIGID', 'SRG Requirement', 'Requirement', 'SRG VulDiscussion', 'VulDiscussion', 'Status', 'SRG Check', 'Check', 'SRG Fix', 'Fix', 'Severity', 'Mitigation', 'Artifact Description', 'Status Justification'

Vulcan column ordering for DISA Excel Exports is:

'IA Control', 'CCI', 'SRGID', 'STIGID', 'Severity', 'SRG Requirement', 'Requirement', 'SRG VulDiscussion', 'VulDiscussion', 'Status', 'SRG Check', 'Check', 'SRG Fix', 'Fix', 'Status Justification', 'Mitigation', 'Artifact Description', 'Vendor Comments'

The 'Severity', 'Mitigations', 'Status Justification', and 'Artifact Description' columns are out of order.

To correct this:
Update the ordering for the headers configured under vulcan/app/constants/export_constants.rb DISA_EXPORT_HEADERS.
Update the ordering for the records under vulcan/app/models/rule.rb, def csv_attributes.

This change affects the column ordering for CSV, Excel and DISA Excel Exports, as all 3 export methods use the same base header and record definitions. If non-DISA Excel Exports are required to follow the current column ordering, additional work will be necessary to break out the header and record definitions into unique definitions for each export type.

[aaronlippold]

I will review this over the next day or two. Thank you for the issue and the PR! 👍🏻