Proposal: Use Node.js's built-in 'querystring' module instead of 'qs'

The qs library is currently used to serialize query strings. The library has previously been free of dependencies, but version 6.10 added a multitude of them. In fact, a large part of googleapis-common's dependency tree now comes from qs:

(Reference: https://npmgraph.js.org/?q=googleapis-common#zoom=w&select=exact%3Aqs%406.12.3)

Describe the solution you'd like

I suggest replacing the qs module with Node.js's built-in querystring module.

The built-in module is battle-tested, used by Gaxios, and supported since very early versions of Node.js. It was momentarily marked as "legacy" (different to "deprecated"), but the decision has since been reverted: nodejs/node#44911.

There are also potential performance benefits. The above issue links to a performance comparison of different querystring serializers that shows querystring outperforming other competitors (including qs): https://github.com/anonrig/fast-querystring

The change can likely be done in a backwards compatible way. Like qs (as it is used in this library), querystring does serialize string arrays like myParams: ['one', 'two'] as 'myParams=one&myParams=two', as described in this code comment:

nodejs-googleapis-common/src/apirequest.ts

Lines 183 to 185 in 459f034

    
           // When forming the querystring, override the serializer so that array 
        
           // values are serialized like this: 
        
           // myParams: ['one', 'two'] ---> 'myParams=one&myParams=two'

It can be also configured to encode spaces as %20 instead of + like described in this code comment:

nodejs-googleapis-common/src/apirequest.ts

Lines 186 to 187 in 459f034

    
           // This serializer also encodes spaces in the querystring as `%20`, 
        
           // whereas the default serializer in gaxios encodes to a `+`.

Unlike querystring, qs does support serializing arbitrarily nested objects, but this is likely not relevant given that the GaxiosOptions.paramsSerializer type doesn't allow them.

I have submitted a pull request #564 that suggests a way to implement this change.

Describe alternatives you've considered

Other options include:

Using the web standard URLSearchParams, supported since Node.js 10. However, according to a member of the Node.js performance team:

URLSearchParams has significant performance issues. I would actually recommend to use node native querystring implementation. We purposefully removed the deprecation tag so that people dont think legacy means broken.

(See: es-tooling/ecosystem-cleanup#7 (comment))
Limiting the qs version range to 6.9.x.

Additional context

This library and its dependency to qs has been mentioned in the JS ecosystem cleanup repository issue here: es-tooling/ecosystem-cleanup#7

	// When forming the querystring, override the serializer so that array
	// values are serialized like this:
	// myParams: ['one', 'two'] ---> 'myParams=one&myParams=two'

	// This serializer also encodes spaces in the querystring as `%20`,
	// whereas the default serializer in gaxios encodes to a `+`.