Support `many-to-many` relationships

[grantfitzsimmons]

This has come up most recently with users asking to use the Project table. Because it has a many-to-many relationship from Collection Object, it is not supported.

• Project is not showing up on Collection Object data entry forms #1172
  • When this is added on the form, an error in the console shows unhandled relationship type: many-to-many
• Can not query Projects from Collection Object #2316
  • Running a query on the projects relationship field throws an error: type object 'CollectionObject' has no attribute 'projects'

A big issue is that this relationship is used infrequently with user-facing tables. Do the programmers have any thoughts on how we can resolve this?

[grantfitzsimmons]

Iñigo at CSIC is also requesting this functionality to be added

[maxpatiiuk]

Could be done as part of #2621

[grantfitzsimmons]

We would like to add a form access to the Project table. The relation should be 1:Project to many Col Objects. The button should be in Colletions Object form near to CollectionObjectCitations. The fields active in the Project table should be: projectName; projectNumber; projectDescription; startDate ;endDate; remarks; GrantAgency

Requested by: Barcelona

[grantfitzsimmons]

CSIC, SAIAB, UMich, New Brunswick, Barcelona, and on and on have been requesting this. Is this a major addition to Sp7?

[grantfitzsimmons]

From @tlammer in #1172:

Reported by UMich

they tried to add projects to the CO form, it appears in 6 but not in 7.
Code added:
cell type="subview" viewname="Project" id="proj" name="projects" initialize="btn=true"

error in the console:
unhandled relationship type: many-to-many

[grantfitzsimmons]

UMich asked again today about the Project subview in Specify 7