Prevent approval of invoice when organization IS NOT a vendor

Purpose: The library should not be able to order from or pay non-vendor organizations by mistake. Approving an invoice for a non-vendor would only happen by mistake

Requirements/Scope:
Prevent approval of invoice when it referencing a non-vendor organization

Approach:
Fail approval and return response with error code organizationIsNotVendor when an invoice referencing a non-vendor organization

Acceptance criteria:

• Logic updated
• Unit tests
• API tests