Make email.SesThrottle handle unlimited quota

Per:

- https://docs.aws.amazon.com/ses/latest/APIReference-V2/API_SendQuota.html

  Max24HourSend

  The maximum number of emails that you can send in the current AWS
  Region over a 24-hour period. A value of -1 signifies an unlimited
  quota. (This value is also referred to as your sending quota.)

email/throttle.go

@@ -61,7 +61,7 @@ func NewSesThrottle(
 func (t *SesThrottle) BulkCapacityAvailable(
 	ctx context.Context, numToSend int,
 ) (err error) {
-	if err = t.refresh(ctx); err != nil {
+	if err = t.refresh(ctx); err != nil || t.unlimited() {
 		return
 	} else if (t.MaxBulkSendable - t.SentLast24Hours) < numToSend {
 		const errFmt = "%w: %d total send max, %s desired bulk capacity, " +
@@ -82,7 +82,7 @@ func (t *SesThrottle) BulkCapacityAvailable(
 func (t *SesThrottle) PauseBeforeNextSend(ctx context.Context) (err error) {
 	if err = t.refresh(ctx); err != nil {
 		return
-	} else if t.SentLast24Hours >= t.Max24HourSend {
+	} else if !t.unlimited() && t.SentLast24Hours >= t.Max24HourSend {
 		err = fmt.Errorf(
 			"%w: %d max, %d sent",
 			ErrExceededMax24HourSend,
@@ -103,6 +103,10 @@ func (t *SesThrottle) PauseBeforeNextSend(ctx context.Context) (err error) {
 	return
 }
 
+func (t *SesThrottle) unlimited() bool {
+	return t.Max24HourSend == -1
+}
+
 func (t *SesThrottle) refresh(ctx context.Context) (err error) {
 	now := t.Now()
 

email/throttle_test.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math"
 	"testing"
 	"time"
 
@@ -84,11 +85,21 @@ func TestNewSesThrottleIncludingRefresh(t *testing.T) {
 		assert.Equal(t, time.Second, f.sleepDuration)
 		assert.Equal(t, f.refresh, throttle.RefreshInterval)
 		assert.Equal(t, int(f.quota.Max24HourSend), throttle.Max24HourSend)
+		assert.Assert(t, throttle.unlimited() == false)
 		assert.Equal(t, int(f.quota.SentLast24Hours), throttle.SentLast24Hours)
 		assert.Equal(t, f.capacity.Value(), throttle.MaxBulkCapacity.Value())
 		assert.Equal(t, 37500, throttle.MaxBulkSendable)
 	})
 
+	t.Run("SucceedsWithUnlimitedQuota", func(t *testing.T) {
+		f := newSesThrottleFixture()
+		f.quota.Max24HourSend = float64(-1)
+
+		throttle, err := f.NewSesThrottle()
+		assert.NilError(t, err)
+		assert.Assert(t, throttle.unlimited() == true)
+	})
+
 	t.Run("FailsIfRefreshFails", func(t *testing.T) {
 		f := newSesThrottleFixture()
 		f.client.getAccountError = errors.New("test error")
@@ -148,6 +159,15 @@ func TestBulkCapacityAvailable(t *testing.T) {
 		assert.NilError(t, err)
 	})
 
+	t.Run("AlwaysSucceedsIfUnlimited", func(t *testing.T) {
+		f, throttle := setup(t)
+		throttle.Max24HourSend = -1
+
+		err := throttle.BulkCapacityAvailable(f.ctx, math.MaxInt)
+
+		assert.NilError(t, err)
+	})
+
 	t.Run("ErrorsIfRefreshFails", func(t *testing.T) {
 		f, throttle := setup(t)
 		numToSend := throttle.MaxBulkSendable - throttle.SentLast24Hours
@@ -215,6 +235,17 @@ func TestPauseBeforeNextSend(t *testing.T) {
 		assert.Equal(t, throttle.Max24HourSend, throttle.SentLast24Hours)
 	})
 
+	t.Run("SucceedsWithUnlimitedQuota", func(t *testing.T) {
+		f, throttle := setup(t)
+		throttle.Max24HourSend = -1
+		throttle.SentLast24Hours = math.MaxInt - 1
+
+		err := throttle.PauseBeforeNextSend(f.ctx)
+
+		assert.NilError(t, err)
+		assert.Equal(t, math.MaxInt, throttle.SentLast24Hours)
+	})
+
 	t.Run("ErrorsIfRefreshFails", func(t *testing.T) {
 		f, throttle := setup(t)
 		f.now = throttle.Updated.Add(f.refresh)