Add service account key file for data provider

[d33bs]

This PR adds a service account key file for use with authentication for a data provider associated with the bucket. This file is being added in to help enable the use of the bucket where there may be issues otherwise. Various other documentation updates were also provided.

Please don't hesitate to let me know if you have any questions. Thank you for any feedback or thoughts you may have!

CC @MikeLippincott

[d33bs]

Thank you @gwaybio ! Merging this in now. I plan to apply the Terraform changes using the -target flag to ensure the existing Google accounts retain their access via the original IAM rules. The terraform plan and terraform apply commands will look something like this: terraform -chdir=terraform/operations [plan|apply] -target=local_file.service_account_key -target=google_service_account_key.key