docs: samples and tests for auto-generated createDatabase and createInstance APIs.

[rahul2393]

Notes

• Adds samples and tests for auto-generated createDatabase and createInstance APIs.
• The sample code style is mostly consistent with our existing samples.
• A new file path has been intentionally introduced so that the samples don't get updated immediately on public documentation - https://cloud.google.com/spanner/docs/create-manage-databases.

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/samples/admin/samples.py:31, tag spanner_create_instance
• samples/samples/admin/samples.py:64, tag spanner_create_database_with_default_leader

---

This comment is generated by snippet-bot.
If you find problems with this result, please file an issue at:
https://github.com/googleapis/repo-automation-bots/issues.
To update this comment, add snippet-bot:force-run label or use the checkbox below:

• Refresh this comment

[parthea]

Do we want to include the function name in the snippet, where folks have to call the function or do we want to have it as a runnable snippet?

For example, see the snippet below which can be run directly
https://github.com/GoogleCloudPlatform/python-docs-samples/blob/main/automl/snippets/batch_predict.py#L21

Instead of

# [START spanner_create_database_with_default_leader]
def create_database_with_default_leader(instance_id, database_id, default_leader):
    """Creates a database with tables with a default leader."""

we could have

def create_database_with_default_leader(instance_id, database_id, default_leader):
    """Creates a database with tables with a default leader."""
    # [START spanner_create_database_with_default_leader]
    from google.cloud import spanner

    # TODO(developer): Uncomment and set the following variables
    # instance_id = "<replace with useful text for developer>"
    # database_id = "<replace with useful text for developer>"
    # default_leader =  "<replace with useful text for developer>"
    spanner_client = spanner.Client()

[rahul2393]

Thanks @parthea, I want to have one change at a time for this work, and follow the syntax above in separate PR for all samples in repository.

[harshachinta]

This python file should be run as main program since this will get referred in the Getting started with Python guide.
Can we add it similar to existing one in snippets.py?

python-spanner/samples/samples/snippets.py

Line 2799 in f3b23b2

if __name__ == "__main__": # noqa: C901

[rahul2393]

This is planned in another PR when we switch the tags later to new samples.

[harshachinta]

nit: The request here can be either dict or spanner_database_admin.CreateDatabaseRequest.
Can we use spanner_database_admin.CreateDatabaseRequest instead of dict, since it will help customers understand how to use autogenerated code for building requests.