feat: add dual region bucket support and sample

[cojenco]

Add dual region bucket support and sample

• method client.create_bucket() accepts a dual-region location as a string with 2 regions concatenated with a '+' (e.g. "US-EAST1+US-WEST1")
• system test verifies a dual region bucket with specified regions can be created with correct location and location_type
• create dual region bucket sample

Fixes #739 🦕

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• samples/snippets/storage_create_bucket_dual_region.py:23, tag storage_create_bucket_dual_region

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[danielbankhead]

LGTM, one nit - we'll want to update references from 'dual region' to 'dual-region'

[cojenco]

Update - Python samples projects have been added to the allowlist (internal cl/438869140). Awaiting for deployment in the next 2 weeks.

[cojenco]

LGTM, one nit - we'll want to update references from 'dual region' to 'dual-region'

@danielbankhead thanks for the review! Do you mean updating the docstrings in client.py?

[danielbankhead]

Yep, correct

[cojenco]

Yep, correct

Updated the docstrings and the docs link as discussed in java thread.

[cojenco]

Note(04.06.2022): Dual-region storage is currently a Pre-GA feature https://cloud.google.com/storage/docs/dual-regions

[andrewsg]

May I suggest the following:

(Optional) The location of the bucket. If not passed, the default location, 'US', will be used. If specifying a dual-region location, the regions can be specified by joining them with a plus sign, for example 'US-CENTRAL1+US-WEST1'. See:
https://cloud.google.com/storage/docs/locations