Create Fidesops Email Connector and Example Email Dataset

[pattisdr]

Is your feature request related to a specific problem?

Add the scaffolding for a new EmailConnector that will eventually send an email to a user to complete an action, instead of accessing a database or a third party endpoint automatically.

Describe the solution you'd like

• Create a Fidesops EmailConnector class (inheriting from BaseConnector
  • Stub out query_config, create_client, close, test_connection, retrieve_data, and mask_data for now.
• Add a schema migration that adds an "email" ConnectionType, so we can create email ConnectionConfigs
• Flesh out an EmailSchema describing the types of secrets we should add to the Email ConnectionConfig. This will probably be very similar or identical to the EmailConfigRequest schema.
• Create an example "email" dataset for use in testing. This will be similar to the existing "manual" dataset.
• Add API tests verifying that we can create email ConnectionConfigs and add secrets to to the ConnectionConfig

Describe alternatives you've considered, if any

A description of any alternative solutions or features you've considered.

Additional context

Add any other context or screenshots about the feature request here.