v4 API: Forms

[n7studios]

Summary

Adds support for endpoints in the forms section of the v4 API.

Testing

• testGetFormSubscriptionsWithBouncedSubscriberState: Test that get_form_subscriptions() returns the expected data when a valid Form ID is specified and the subscription status is cancelled.
• testGetFormSubscriptionsWithAddedAfterParam: Test that get_form_subscriptions() returns the expected data when a valid Form ID is specified and the added_after parameter is used.
• testGetFormSubscriptionsWithAddedBeforeParam: Test that get_form_subscriptions() returns the expected data when a valid Form ID is specified and the added_before parameter is used.
• testGetFormSubscriptionsWithCreatedAfterParam: Test that get_form_subscriptions() returns the expected data when a valid Form ID is specified and the created_after parameter is used.
• testGetFormSubscriptionsWithCreatedBeforeParam: Test that get_form_subscriptions() returns the expected data when a valid Form ID is specified and the created_before parameter is used.
• testGetFormSubscriptionsPagination: Test that get_form_subscriptions() returns the expected data when a valid Form ID is specified and pagination parameters and per_page limits are specified.
• testGetFormSubscriptionsWithInvalidFormID: Test that get_form_subscriptions() throws a ClientException when an invalid Form ID is specified.
• testGetFormSubscriptionsWithInvalidSubscriberState: Test that get_form_subscriptions() throws a ClientException when an invalid subscriber state is specified.
• testGetFormSubscriptionsWithInvalidPagination: Test that get_form_subscriptions() throws a ClientException when invalid pagination parameters are specified.
• testAddSubscriberToFormByID: Test that add_subscriber_to_form_by_subscriber_id() returns the expected data.
• testAddSubscriberToFormByIDWithInvalidFormID: Test that add_subscriber_to_form_by_subscriber_id() throws a ClientException when an invalid form ID is specified.
• testAddSubscriberToFormByIDWithInvalidSubscriberID: Test that add_subscriber_to_form_by_subscriber_id() throws a ClientException when an invalid email address is specified.

Removed Tests:

• testAddSubscriberToFormWithFirstName
• testAddSubscriberToFormWithCustomFields
• testAddSubscriberToFormWithTagID

v4 API has no concept of adding a new subscriber to a form with data; a separate PR will be added to add support for the new Create a subscriber endpoint (https://developers.convertkit.com/v4.html#create-a-subscriber), which supports this.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• The code passes when running PHPStan
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

[noelherrick]

Looks good! What are your thoughts on passing along existing vs. new to the API consumer? The API will return a 200 if the subscriber is already subscribed vs. a 201 if it is not.

[n7studios]

Looks good! What are your thoughts on passing along existing vs. new to the API consumer? The API will return a 200 if the subscriber is already subscribed vs. a 201 if it is not.

This PR exposes the response object, allowing the consumer to inspect the HTTP status code, should they wish to determine whether a subscriber is already subscribed vs. created:

$result = $api->add_subscriber_to_form(12345, 'joe.bloggs@convertkit.com');
$code = $api->getResponseInterface()->getStatusCode(); // 200 OK if e.g. a subscriber already added to the specified form, 201 Created if the subscriber added to the specified form for the first time.