Table to Table relationships where there is a many to many

You can place standard multi-select lists in the Details table for solicitation, contracts, maintenance, or, you can mimic the model of Address >> has many >> Details and Provider >> has many >> Details. You can do Contractor >> has many >> Details, and Maintenance >> has Many Details. 

The object is to make your unique data stay unique. If you need to do Provider maintenance, that is done in the Provider table; Address maintenance, the Address table. Actual work orders would be created in the Details table.