Add "Add to newsletter" feature

== INCOMPLETE/DESIGN IN PROCESS ==

Problem/Motivation

When a donor donates, we want the ability to add them to an external newsletter service.

Proposed resolution

Create an post-donation event that sends the email to an event subscriber.

• Define an event such as:
final class DonationEvent
{

/**
* Name of the event fired after a donation.
*
* @Event
*
* @var string
*/
const POST_DONATION = 'campaign_kit:post_donation';

private addToNewsletter: "Standard"
private newsletterLists: (add array value of "Main")
private isSuccessful: (use TRUE or FALSE depending on whether the donation went through)
private resultCode:
private donerEmail:
private donationAmount:
private donationType:
private donerFirstName:
private donerLastName:

}

-- Process --

1. When the general config Ask to add to newsletter checkbox is enabled, set the campaign Ask to add to newsletter to "Standard". Otherwise, set it to "None".
2. When creating the campaign, copy the "Default Newsletter ID" into the campaign Newsletter ID.
3. In the custom SFIC custom event subscriber, place a switch statement that is based on the campaign Newsletter ID. Leave the case "MailChimp" empty for now.

Remaining tasks

User interface changes

-- General Configuration --

1. Add a textfield (16 chars) on the general CK configuration page: "Ask to add to newsletter?"
2. Add a textfield (64 chars) on the general CK configuration page: "Default Newsletter ID."

-- Campaign Form (for campaign administrators) --

1. Add a textfield (16 chars) to the campaigns that only an administrator can see: "Ask to add to newsletter?"
2. Add a textfield (64 chars) on the the campaigns for "Newsletter ID".

Data model changes

-- General Configuration --

1. Add a textfield (16 chars) on the general CK configuration page: "Ask to add to newsletter?"
2. Add a textfield (64 chars) on the general CK configuration page: "Default Newsletter ID."

-- Campaign Form (for campaign administrators) --

1. Add a textfield (16 chars) to the campaigns that only an administrator can see: "Ask to add to newsletter?"
2. Add a textfield (64 chars) on the the campaigns for "Newsletter ID".