Document configurable properties

[jensgreen]

I recently had to modify one of the properties below by setting a TeamCity internal property.

The property was undocumented, and I had to find it by searching the source code.

I would have expected to find important properties to be documented in the Configuration section of the README.

teamcity-google-storage/google-storage-common/src/main/kotlin/jetbrains/buildServer/serverSide/artifacts/google/GoogleConstants.kt

Lines 21 to 37 in b892570

	object GoogleConstants {
	const val STORAGE_TYPE = "google-storage"
	const val SETTINGS_PATH = "google-storage-settings"
	const val SIGNED_URL_PATH = "google-signed-urls"
	const val CREDENTIALS_TYPE = "credentials.type"
	const val CREDENTIALS_ENVIRONMENT = "environment"
	const val CREDENTIALS_KEY = "key"
	const val USE_SIGNED_URL_FOR_UPLOAD = "credentials.useSignedUrl"
	const val PARAM_ACCESS_KEY = Constants.SECURE_PROPERTY_PREFIX + "access-key"
	const val PARAM_BUCKET_NAME = "bucket-name"
	const val PATH_PREFIX_ATTR = "google_path_prefix"
	const val PATH_PREFIX_SYSTEM_PROPERTY = "storage.google.path.prefix"
	const val URL_LIFETIME_SEC = "storage.google.url.expiration.time.seconds"
	const val SIGNED_URL_GET_CACHE_ENABLED = "storage.google.signedUrl.get.cache.enabled"
	const val DEFAULT_URL_LIFETIME_SEC = 60
	}