ruby: add AUTHENTICATION.md template

[quartzmo]

Add AUTHENTICATION.md for all GAPIC packages in googleapis/google-cloud-ruby.

[refs googleapis/google-cloud-ruby#2933]

Example usage in a google-cloud-ruby package:

diff --git a/google-cloud-bigquery-data_transfer/synth.py b/google-cloud-bigquery-data_transfer/synth.py
index 15fd8f222..3f1df1cd9 100644
--- a/google-cloud-bigquery-data_transfer/synth.py
+++ b/google-cloud-bigquery-data_transfer/synth.py
@@ -38,6 +38,17 @@ s.copy(v1_library / '.gitignore')
 s.copy(v1_library / '.yardopts')
 s.copy(v1_library / 'google-cloud-bigquery-data_transfer.gemspec', merge=ruby.merge_gemspec)
 
+# Copy common templates
+common_templates = gcp.CommonTemplates()
+metadata = {
+    "package_name": "google-cloud-bigquery-data_transfer",
+    "module_name": "Bigquery::DataTransfer",
+    "module_name_credentials": "Bigquery::DataTransfer::V1",
+    "constant_name": "DATA_TRANSFER",
+}
+templates = common_templates.ruby_library(metadata=metadata)
+s.copy(templates)
+
 # PERMANENT: Use custom credentials env variable names
 s.replace(
     'lib/google/cloud/bigquery/data_transfer/v1/credentials.rb',

[quartzmo]

To demo this template in google-cloud-ruby:

1. Checkout the branch for this PR to synthtool.
2. pip install -e ./synthtool
3. cd google-cloud-ruby/google-cloud-asset
4. python -m synthtool

[blowmage]

Is this the direction we want to take? Do we want the templates to be part of this tool? Or should the template be somewhere on the repo?

[TheRoyalTnetennba]

Should this open with a best-practices quickstart?

[quartzmo]

@TheRoyalTnetennba Is there one available that I can drop in? Or adapt? (If so please link)

[TheRoyalTnetennba]

Is this the direction we want to take? Do we want the templates to be part of this tool? Or should the template be somewhere on the repo?

I have mixed feelings about this, but I think this approach works well for both split/monorepo, whereas if we ERB'd it in our own repo, we'd end up having our own separate tool in the event of a repo split (at least as I'm imaging how it would work).

[blowmage]

I definitely think generating this file in GAPIC is preferred. I guess my question is if putting the template in this tool is acceptable for the short term.

[TheRoyalTnetennba]

@quartzmo I don't know of one. I think inserting some Overview/Quickstart like the following just above Project and Credential Lookup would be nice for people just looking for a quick how-to:

Quickstart

1. Create and download a service account
2. Set the environment variable: export {{ metadata["constant_name"] }}_CREDENTIALS=/path/to/json
3. Initialize client:

require "{{ metadata["package_name"].replace("-", "/") }}"

client = Google::Cloud::{{ metadata["module_name"] }}.new

[quartzmo]

It sounds like this is the right home for the template for now, so I will update the template for @TheRoyalTnetennba's suggestions.

[quartzmo]

I will also test synthtool's Ruby support for .repo-metadata.json, and update if needed.

[quartzmo]

@TheRoyalTnetennba I updated this PR to use values from .repo-metadata.json. The values needed for the template are:

{
  "name": "google-cloud-bigquery-data_transfer",
  "name_pretty": "BigQuery Data Transfer Service",
  "module_name": "Bigquery::DataTransfer",
  "module_name_credentials": "Bigquery::DataTransfer::V1",
  "env_var_prefix": "DATA_TRANSFER"
}

This reduces the additions needed in synth.py to:

# Copy common templates
templates = gcp.CommonTemplates().ruby_library()
s.copy(templates)

Please give this comment a +1 if this sounds good to you.

[TheRoyalTnetennba]

@quartzmo can you swap "name" for "distribution_name" throughout? The name field should should correspond to the pre-".google-apis.com" name in the googleapis/*.yaml i.e. https://github.com/googleapis/googleapis/blob/9a89b9443aa9d43ccecbd5200cb866e551bbd5e7/google/cloud/bigquery/datatransfer/datatransfer.yaml#L3 . Whereas distribution_name should be just whatever appears after gem install

[quartzmo]

@TheRoyalTnetennba Done. The keys needed in .repo-metadata.json now look like this:

{
  "distribution_name": "google-cloud-bigquery-data_transfer",
  "module_name": "Bigquery::DataTransfer",
  "module_name_credentials": "Bigquery::DataTransfer::V1",
  "env_var_prefix": "DATA_TRANSFER"
}

[quartzmo]

@TheRoyalTnetennba Do you know who should approve this PR for merging?

[quartzmo]

@TheRoyalTnetennba I'll merge when you approve.

[TheRoyalTnetennba]

This is awesome

[quartzmo]

When can we expect this addition to be released?

[busunkim96]

@quartzmo Autosynth runs the synthtool at master, so a new release shouldn't be necessary. The synth.py scripts just need to be updated to copy over the templates.

templates = common_templates.ruby_library(metadata=metadata)
s.copy(templates)

[quartzmo]

@busunkim96 Great, thanks! I'll open a PR in google-cloud-ruby to update the synth.py scripts and add the .repo-metadata.json files.