Check active subscriptions before starting Office365 crawler

[bbenner7635]

Description

Check active subscriptions before starting Office365 crawler

Occassionally, if a user has multiple pipelines sharing credentials, startSubscriptions get get throttled on startup:

Caused by: java.lang.SecurityException: Access forbidden: 403 Forbidden: "{"error":{"code":"429","message":"Too many frequent subscription start requests. Please retry again after 8m 46s."}}"
	at org.opensearch.dataprepper.plugins.source.microsoft_office365.RetryHandler.executeWithRetry(RetryHandler.java:44)
	at org.opensearch.dataprepper.plugins.source.microsoft_office365.Office365RestClient.startSubscriptions(Office365RestClient.java:105)

By calling listSubscriptions first, the crawler plugin will only start subscriptions for content types which are not yet enabled and thereby reducing risk of startup failure.

Moreover, if listSubscriptions fails after retry, fallback to calling startSubscriptions anyway.

Tested locally by disabling some content types and starting the pipeline:

2025-11-01T19:37:22,282 [test-pipeline-sink-worker-2-thread-1] INFO  org.opensearch.dataprepper.plugins.source.microsoft_office365.Office365RestClient - Content type Audit.Exchange needs to be started
2025-11-01T19:37:23,997 [test-pipeline-sink-worker-2-thread-1] INFO  org.opensearch.dataprepper.plugins.source.microsoft_office365.Office365RestClient - Content type Audit.SharePoint needs to be started
2025-11-01T19:37:35,374 [pool-3-thread-1] INFO  org.opensearch.dataprepper.plugins.aws.AwsSecretsSupplier - Finished retrieving latest secret in aws:secrets:office365-credentials.
2025-11-01T19:37:36,182 [test-pipeline-sink-worker-2-thread-1] INFO  org.opensearch.dataprepper.plugins.source.microsoft_office365.Office365RestClient - Successfully started 2 subscription(s)

Issues Resolved

N/A

Check List

• New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
  • New functionality has javadoc added
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