Added docs for quota project (#6054)

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References dbt-labs/dbt-bigquery#1343 dbt-labs/dbt-bigquery#1344

Adding docs to detail changes in PR dbt-labs/dbt-bigquery#1345

This adds detail about how to override the `quota_project` through the
dbt profile. It also updates the information regarding the execution
project. I believe that the execution project just sets where the BQ job
is created and doesn't actually impact where it's billed from (I could
be wrong on this, but from my testing I can see that the quota project
is set from the environment not from the execution project override
currently detailed in the docs).

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---------

Co-authored-by: Leona B. Campbell <[email protected]>
Co-authored-by: Matt Shaver <[email protected]>

website/docs/docs/core/connect-data-platform/bigquery-setup.md

@@ -388,6 +388,28 @@ my-profile:
       execution_project: buck-stops-here-456
 ```
 
+### Quota project
+
+By default, dbt will use the `quota_project_id` set within the credentials of the account you are using to authenticate to BigQuery.
+
+Optionally, you may specify `quota_project` to bill for query execution instead of the default quota project specified for the account from the environment.
+
+This can sometimes be required when impersonating service accounts that do not have the BigQuery API enabled within the project in which they are defined. Without overriding the quota project, it will fail to connect.
+
+If you choose to set a quota project, the account you use to authenticate must have the `Service Usage Consumer` role on that project.
+
+```yaml
+my-profile:
+  target: dev
+  outputs:
+    dev:
+      type: bigquery
+      method: oauth
+      project: abc-123
+      dataset: my_dataset
+      quota_project: my-bq-quota-project
+```
+
 ### Running Python models on Dataproc
 
 import BigQueryDataproc from '/snippets/_bigquery-dataproc.md';