Update CHANGELOG.md (#1895)

* Update CHANGELOG.md

* add entries for previously-reverted resources; formatting

* add entry for cherry-picked bugfix

Author: danawillow

CHANGELOG.md

@@ -1,4 +1,24 @@
 ## 3.15.0 (Unreleased)
+
+FEATURES:
+* **New Resource:** `google_compute_instance_group_named_port` ([#1869](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1869))
+* **New Resource:** `google_service_usage_consumer_quota_override` ([#1884](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1884))
+* **New Resource:** `google_firebase_project`: enables Firebase for a referenced Google project ([#1885](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1885))
+* **New Resource:** `google_iap_brand` ([#1848](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1848))
+* **New Resource:** `google_iap_client` ([#1848](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1848))
+* **New Resource:** `google_appengine_flexible_app_version` ([#1849](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1849))
+
+IMPROVEMENTS:
+* accesscontextmanager: Added `regions` field to `google_access_context_manager_access_level` ([#1882](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1882))
+* compute: added support for IAM conditions in `google_compute_subnet_iam_*` IAM resources ([#1877](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1877))
+* kms: Added new field "Additional Authenticated Data" for Cloud KMS data source `google_kms_secret` ([#1886](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1886))
+* kms: Added new field "Additional Authenticated Data" for Cloud KMS resource `google_kms_secret_ciphertext` ([#1886](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1886))
+
+BUG FIXES:
+* kms: Fixed an issue in `google_kms_crypto_key_version` where `public_key` would return empty after apply ([#1879](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1879))
+* logging: Fixed import issue with `google_logging_metric` in a non-default project. ([#1876](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1876))
+* provider: Fixed an error with resources failing to upload large files (e.g. with `google_storage_bucket_object`) during retried requests ([#1894](https://github.com/terraform-providers/terraform-provider-google-beta/pull/1894))
+
 ## 3.14.0 (March 23, 2020)
 
 FEATURES: