Ds 379 canada sso registration

#### What's this PR do?
- Utilizes Canada SSO registration in `dosomething_canada` module
- Improves and extends Canada integration tests

#### How should this be manually tested?
- Enable and setup Dosomething Canada module
- Run `ds test canada`  

#### What are the relevant tickets?
- Part of [#DS-379](https://jira.dosomething.org/browse/DS-379): Move functionality common to UK and Canada to the new nodule
- #3176: Canada SSO: adapt login to common flow provided in external_auth
- #3174: UK SSO: adapt login/signup to common flow provided in external_auth
- dosomething/drupal-external-auth#2