[sitecore-jss] GraphQL Client Retry Improvements

[addy-pathania]

• This PR follows the Contribution Guide
• Changelog updated

Description / Motivation

• Handle additional scenarios, now we are able to handle string error codes. By default the DefaultRetryStrategy handles common error codes like ECONNRESET, ETIMEDOUT and EPROTO but other codes can be configured using the same.
• retries has now been enabled by default with a default value of 3. It can be disabled for all the services by configuring the env variable i.e GRAPH_QL_SERVICE_RETRIES to 0. We can also disable retries per service by configuring it to 0 inside the service-factory file in the app.
• [Retry-After] header now falls back to the default delay time when it comes out to be empty.

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[illiakovalenko]

Looks nice 👍
Please, take a look at my comments/suggestions below
Some parts can improved/refactored so will be easier to maintain "retries" unit tests moving further

[illiakovalenko]

Please, review the new comments I left in our discussions

[ambrauer]

Looks great 👍Just a couple jsdoc suggestions.

[addy-pathania]

@illiakovalenko FYI me and Adam had a discussion about the error type and we decided to revert back to almost similar implementation which we had in the beginning of this PR. We have introduced a GraphQLClientError type which is the intersection of the partial of ClientError and 'code' from NodeJS.ErrorException type. This way we and the user would not have to worry about the type guards or the type checking and can easily implement a custom solution. We can think about implementing our own error types in future when we get rid of the graphql request client.

[illiakovalenko]

The solution using Partial looks good 👍
Added another comment below, after that feel free to merge