Make CampaignId available as a session scope variable

Summary

Adding the CampaignId as a session variable will make able to add contextual analysis at the Campaign analysis tab from Campaigns.

Content

As we've made with some other business objects (contacts, accounts, custom...), we aimed to add an OBI analysis in the analysis tab of the Campaign object (not sales campaign but marketing ones). There was a campaign analysis tab [Image below point 1] that by default roots to an unexisting address of OBI ("/shared/Sales/Analytic Library/Embedded Content/_portal/Campaign Members/dashboard layout")[Image below point 3]. So we created a custom analysis, and added the CampaignId as a prompted filter to make it available at the page composer [Image below point 2].