Handle 503 retries where the Retry-After header exceeds what the Graph SDK will wait for (#2888)

This logic will only trigger if the Graph retry handler does not handle the 503 (it is invoked first).

We remove the check in Corso for `absoluteMaxDelay` because our retry config will not trigger that limit (180s).
This allows the retry to kick in if the 503 response contains a `Retry-After` value > 180s

This could help with issues like https://github.com/alcionai/corso/issues/2876

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [x] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

#### Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* #2876 

#### Test Plan

<!-- How will this be tested prior to merging.-->
- [x] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

src/internal/connector/graph/retry_middleware.go

@@ -35,8 +35,7 @@ func (middleware RetryHandler) retryRequest(
 ) (*http.Response, error) {
 	if (respErr != nil || middleware.isRetriableErrorCode(req, resp.StatusCode)) &&
 		middleware.isRetriableRequest(req) &&
-		executionCount < middleware.MaxRetries &&
-		cumulativeDelay < time.Duration(absoluteMaxDelaySeconds)*time.Second {
+		executionCount < middleware.MaxRetries {
 		executionCount++
 
 		delay := middleware.getRetryDelay(req, resp, exponentialBackoff)
@@ -71,7 +70,7 @@ func (middleware RetryHandler) retryRequest(
 }
 
 func (middleware RetryHandler) isRetriableErrorCode(req *http.Request, code int) bool {
-	return code == http.StatusInternalServerError
+	return code == http.StatusInternalServerError || code == http.StatusServiceUnavailable
 }
 
 func (middleware RetryHandler) isRetriableRequest(req *http.Request) bool {

src/internal/connector/graph/service.go

@@ -27,12 +27,10 @@ import (
 const (
 	logGraphRequestsEnvKey    = "LOG_GRAPH_REQUESTS"
 	log2xxGraphRequestsEnvKey = "LOG_2XX_GRAPH_REQUESTS"
-	numberOfRetries           = 3
 	retryAttemptHeader        = "Retry-Attempt"
 	retryAfterHeader          = "Retry-After"
 	defaultMaxRetries         = 3
 	defaultDelay              = 3 * time.Second
-	absoluteMaxDelaySeconds   = 180
 	rateLimitHeader           = "RateLimit-Limit"
 	rateRemainingHeader       = "RateLimit-Remaining"
 	rateResetHeader           = "RateLimit-Reset"
@@ -309,7 +307,7 @@ func (handler *LoggingMiddleware) Intercept(
 	msg := fmt.Sprintf("graph api error: %s", resp.Status)
 
 	// special case for supportability: log all throttling cases.
-	if resp.StatusCode == http.StatusTooManyRequests {
+	if resp.StatusCode == http.StatusTooManyRequests || resp.StatusCode == http.StatusServiceUnavailable {
 		log.With(
 			"limit", resp.Header.Get(rateLimitHeader),
 			"remaining", resp.Header.Get(rateRemainingHeader),