feat(spanner): add samples for database roles

[varuncnaik]

Adds samples with database roles on requests.

[varuncnaik]

I'll work on a sample for ListDatabaseRoles soon.

[snippet-bot[bot]]

Here is the summary of changes.

You are about to add 4 region tags.

• spanner/spanner_snippets/spanner/spanner_add_and_drop_database_role.go:17, tag spanner_add_and_drop_database_role
• spanner/spanner_snippets/spanner/spanner_enable_fine_grained_access.go:17, tag spanner_enable_fine_grained_access
• spanner/spanner_snippets/spanner/spanner_list_database_roles.go:17, tag spanner_list_database_roles
• spanner/spanner_snippets/spanner/spanner_read_data_with_database_role.go:17, tag spanner_read_data_with_database_role

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[enocom]

@varuncnaik Looks like there are some compilation errors caused by missing types. You'll need to upgrade the underlying client if these are new methods and types you're using.

[enocom]

@varuncnaik Still seeing some compilation errors. Let me know if you'd like some help with this. Otherwise, I'll assume you'll ping me when you're ready for another look.

[enocom]

Looks like we're still missing some types:

# github.com/GoogleCloudPlatform/golang-samples/spanner/spanner_snippets
spanner_snippets/snippet.go:825:3: unknown field 'DatabaseRole' in struct literal of type "cloud.google.com/go/spanner".ClientConfig
# github.com/GoogleCloudPlatform/golang-samples/spanner/spanner_snippets/spanner
spanner_snippets/spanner/spanner_read_data_with_database_role.go:32:3: unknown field 'DatabaseRole' in struct literal of type "cloud.google.com/go/spanner".ClientConfig

@varuncnaik Want some help finishing this? We've had this open for quite awhile now.

[varuncnaik]

Hi @enocom, we're aware of the missing types. In my local setup for this PR, I'm editing my go.mod file to replace cloud.google.com/go/spanner with my local copy of https://github.com/googleapis/google-cloud-go/pull/5701.

We plan to merge both of these PRs around the time that Cloud Spanner fine-grained access control becomes generally available. Until then, I am periodically merging the latest main into both PRs and making sure that tests pass locally. CC @rahul2393, in case the two of you want to exchange information over DM.

[enocom]

Sounds good. Just ping me when you're ready and we can merge this.