Add intercom custom attributes

[tspenov]

Changes

custom_attributes:
paid_active_subscription: true/false
trialing_subscription: true/false
renewal_upcoming_at: timestamp
subscription_set_to_cancel: true/false
last_active_at: timestamp

Ticket

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have tried to find clearer solution before commenting hard-to-understand parts of code
• I have added tests that prove my fix is effective or that my feature works