Implement #copy_answer! method for all kinds of answers

[#79958812]

Necessary for collaboration.
Create collaboration_runs table

[#79958812]
Implement CollaborationRun model + specs

[#79958812]
Implement CreateCollaboration service + specs

[#79958812]
Propagate answer to collaborators if the current run is a collaboration

[#79958812]
Handle ?collaboration_endpoint_url=<url> argument for activities

[#79958812]

It creates collaboration. It will be refactored, but seems to
work.
Fix answer propagation to collaborators

[#79958812]

... when there are runs related to different activities. This case
happens when collaboration run is created for sequence.
Setup collaboration for sequences, refactor activity collaboration

[#79958812]
Fix / refactor authentication for collaboration needs

[#79958812]
Disable collaboration run when user runs it individually from portal

[#79958812]
Merge branch 'collaboration'

Conflicts:
	db/schema.rb