Adds support for twilio email (sendgrid) dispatch

[eastandwestwind]

Closes #1975

Code Changes

• Adds dispatcher for Twilio Email
• Adds sendgrid client to requirements
• Updates model for Twilio Email to include additional details needed in config

Note- this ticket does not include support for fides templates through sendgrid.

Steps to Confirm

• In config:

FIDES__EXECUTION__SUBJECT_IDENTITY_VERIFICATION_REQUIRED=true
FIDES__NOTIFICATIONS__NOTIFICATION_SERVICE_TYPE="twilio_email"
FIDES__NOTIFICATIONS__SEND_REQUEST_COMPLETION_NOTIFICATION=true
FIDES__NOTIFICATIONS__SEND_REQUEST_RECEIPT_NOTIFICATION=true
FIDES__NOTIFICATIONS__SEND_REQUEST_REVIEW_NOTIFICATION=true

• Set up a Sendgrid test acct
• Use postman to add a new Twilio Email config:

{
    "key": "twilio_email_key",
    "name": "twilio_email",
    "service_type": "twilio_email",
    "details": {
    "twilio_email_from": "[email protected]"
    }
}

• Use postman to add Twilio Email secrets:

{
    "twilio_api_key": "your-api-key"
}

• Submit privacy request and confirm emails are sent

Pre-Merge Checklist

• All CI Pipelines Succeeded
• Documentation:
  • documentation complete, PR opened in fidesdocs
  • documentation issue created in fidesdocs
• Issue Requirements are Met
• Relevant Follow-Up Issues Created
• Update CHANGELOG.md

Description Of Changes

Write some things here about the changes and any potential caveats

[adamsachs]

i think this all looks really good! was able to test successfully (at least to the point of getting an initial verification code) to my email. the updates look very clean and were easy to follow!

i just have a few minor polish points with error handling - let me know what you think.