Link multiple offers to the same project

[sven1103]

Stakeholder request:

As a project manager, i want to link multiple offers to the same project, to account for batch orders in the same project context..

@qbicStefanC please feel free to complement.

[qbicStefanC]

Current alternative example: multi-omics projects for which we ideally generate one offer per omics level and then later would like to link them to the same project in qPortal.