Allow setting gcs_tmp_bucket on GoogleBigQuery class

This parallels more closely the set up of the Redshift class. It also
allows for a more simple implementation when using multiple different
instances of GoogleBigQuery in the same environment.

parsons/google/google_bigquery.py

@@ -143,6 +143,10 @@ class GoogleBigQuery(DatabaseConnector):
             A dictionary containing any requested client options. Defaults to the required
             scopes for making API calls against External tables stored in Google Drive.
             Can be set to None if these permissions are not desired
+        gcs_temp_bucket: str
+            Name of the GCS bucket that will be used for storing data during bulk transfers.
+            Required if you intend to perform bulk data transfers (eg. the copy_from_gcs method),
+            and env variable ``GCS_TEMP_BUCKET`` is not populated.
     """
 
     def __init__(
@@ -157,6 +161,7 @@ def __init__(
                 "https://www.googleapis.com/auth/cloud-platform",
             ]
         },
+        tmp_gcs_bucket: Optional[str] = None,
     ):
         self.app_creds = app_creds
 
@@ -172,6 +177,7 @@ def __init__(
         self.project = project
         self.location = location
         self.client_options = client_options
+        self.tmp_gcs_bucket = tmp_gcs_bucket
 
         # We will not create the client until we need to use it, since creating the client
         # without valid GOOGLE_APPLICATION_CREDENTIALS raises an exception.
@@ -684,7 +690,8 @@ def copy_s3(
                 The GoogleCloudStorage Connector to use for loading data into Google Cloud Storage.
             tmp_gcs_bucket: str
                 The name of the Google Cloud Storage bucket to use to stage the data to load
-                into BigQuery. Required if `GCS_TEMP_BUCKET` is not specified.
+                into BigQuery. Required if `GCS_TEMP_BUCKET` is not specified or set on
+                the class instance.
             template_table: str
                 Table name to be used as the load schema. Load operation wil use the same
                 columns and data types as the template table.
@@ -700,8 +707,12 @@ def copy_s3(
         """
 
         # copy from S3 to GCS
-        tmp_gcs_bucket = check_env.check("GCS_TEMP_BUCKET", tmp_gcs_bucket)
-        gcs_client = gcs_client or GoogleCloudStorage(app_creds=self.app_creds)
+        tmp_gcs_bucket = (
+            tmp_gcs_bucket
+            or self.tmp_gcs_bucket
+            or check_env.check("GCS_TEMP_BUCKET", tmp_gcs_bucket)
+        )
+        gcs_client = gcs_client or GoogleCloudStorage()
         temp_blob_uri = gcs_client.copy_s3_to_gcs(
             aws_source_bucket=bucket,
             aws_access_key_id=aws_access_key_id,
@@ -767,7 +778,8 @@ def copy(
                 the job fails.
             tmp_gcs_bucket: str
                 The name of the Google Cloud Storage bucket to use to stage the data to load
-                into BigQuery. Required if `GCS_TEMP_BUCKET` is not specified.
+                into BigQuery. Required if `GCS_TEMP_BUCKET` is not specified or set on
+                the class instance.
             gcs_client: object
                 The GoogleCloudStorage Connector to use for loading data into Google Cloud Storage.
             job_config: object
@@ -783,7 +795,11 @@ def copy(
                 client.
         """
         data_type = "csv"
-        tmp_gcs_bucket = check_env.check("GCS_TEMP_BUCKET", tmp_gcs_bucket)
+        tmp_gcs_bucket = (
+            tmp_gcs_bucket
+            or self.tmp_gcs_bucket
+            or check_env.check("GCS_TEMP_BUCKET", tmp_gcs_bucket)
+        )
         if not tmp_gcs_bucket:
             raise ValueError(
                 "Must set GCS_TEMP_BUCKET environment variable or pass in tmp_gcs_bucket parameter"