Proposal: support accessing database with fine-grained access control

[toga4]

CLI Option:

spanner-cli -p <project> -i <instance> -d <database> --role <role>

Syntax:

USE <database> WITH ROLE <role>;

https://cloud.google.com/spanner/docs/access-with-fgac?hl=en

[toga4]

Prototype implementation: master...toga4:spanner-cli:feature/with-role

[yfuruyama]

@toga4 Thank you for your proposal. It's a good idea to support fine-grained access control in spanner-cli.

One suggestion: for USE statement, shall we omit WITH word? i.e. USE <database> [ROLE <role>];

Then it will be consistent with other multi-optional statement, like BEGIN [RW] [PRIORITY {HIGH|MEDIUM|LOW}] [TAG <tag>];: https://github.com/cloudspannerecosystem/spanner-cli#syntax

[toga4]

@yfuruyama Sure, let's omit it. Then, syntax will be below.

USE <database> ROLE <role>;

Can I submit a PR with this?

[yfuruyama]

Sure, thank you!

FYI: @apstndb @takabow