Coinbase integration

[timurkhafizov]

• [x] Setup devise OAuth
• [x] Config Coinbase OAuth
• [x] Create Identity and associate it with User
• [x] Refresh all users tokens every 1 hour (because Coinbase access token expires in 2 hours)
• [x] Create Coinbase::Sell and Coinbase::Buy models and associate them with Transaction
• [x] Add service and sidekiq worker to sync user buys
• [x] Add service and sidekiq worker to sync user sells
• [x] Add reccurrent worker to sync all users buys every day at 1AM
• [x] Add reccurrent worker to sync all users sells every day at 1AM
• [ ] Put link somewhere