DE-1146 Release v5

[vtopc]

Breaking changes:

Mailgun client is now domain agnostic

• No need to pass the domain into the func mailgun.NewMailgun
• Many methods now require passing a domain, which indicates which methods are domain-specific and which are global for your account.
  • Pay attention to that func NewMessage(domain, from, subject, text string, to ...string) *PlainMessage has a variadic to argument, so there would be no compile error if you miss passing domain.

Types and mocks

• API requests, responses, and helper types are moved into github.com/mailgun/mailgun-go/v5/mtypes package.
• Event interface and parsers moved to github.com/mailgun/mailgun-go/v5/events
• mocks moved to github.com/mailgun/mailgun-go/v5/mocks to address Remove dependency on github.com/go-chi/chi/v5 (again) #322 and Why does this depend on chi? #332

Validation

• ValidateEmail(...) moved to Mailgun.
• The IsValid field is removed from the response; use Risk.

Subaccounts

• SubaccountDetails(ctx context.Context, subaccountId string) renamed to GetSubaccount(ctx context.Context, subaccountID string) for consistency.

Domains:

• Deprecated func UpdateDomainTrackingWebPrefix is removed, use func UpdateDomain.
• func VerifyAndReturnDomain is removed, use func VerifyDomain.

Metrics

• The deprecated field ESPBlockCount has been removed. Use TemporaryFailedESPBlockCount.

Other changes

These changes might be breaking in some cases.

• Send(ctx context.Context, m SendableMessage) (mes string, id string, err error) now accepts interface.

• SetAPIBase() now returns an error.

• For the EU: do mg.SetAPIBase(mailgun.APIBaseEU) instead of mg.SetAPIBase("https://api.eu.mailgun.net/v...").

• The Webhook Signing Key is optional now and does not relate to the API key. If the Webhook Signing Key is not set(by SetWebhookSigningKey(webhookSigningKey string)), don't call the VerifyWebhookSignature() method, as it will always fail.

• mailgun.MailgunImpl is renamed to mailgun.Client for not stuttering.