Add 429 status code as default to the RetryInterceptor about kohttp

[rybalkinsd]

Hey @doyaaaaaken . Let me give some thoughts.

Please, refer https://httpstatuses.com/429

As for no, we're retrying requests with delay based on invocationTimeout and ratio.
Getting 429 it is possible to retry using slightly different technique:
429 response MAY have a Retry-After: xxx header.
We can use this number (xxx) as a time before next retry.

Also, it m/b a good idea to introduce maxDelayTime

[doyaaaaaken]

Hi, I tried to work on this. And I have one question.

Which does this issue mean?

1. When we get 429 response from external service, we should regard it as error and retry (or stop is better?) to request.
2. When we reach to max retry attempt's count, we should handle this response as 429 status code. (Even if the response code is not 429)

If the meaning is 1, should we simply add 429 on errorStatuses at below code?

kohttp/kohttp/src/main/kotlin/io/github/rybalkinsd/kohttp/interceptors/RetryInterceptor.kt

Line 24 in d6e2434

private val errorStatuses: List<Int> = listOf(503, 504)

If the meaning is 2, I guess we could not rewrite response code because Response.code is final int field.
(And also I think we shouldn't rewrite status code inside kohttp library. It's out of developer's expectation.)