client: setters for JSON and XML Marshal/Unmarshal

[GRbit]

Today I learned that I can set external JSON library for resty to marshal JSON faster. It wasn't so obvious because I haven't read the docs (let's be honest it's not only me who doesn't read docs), but there was no method for resty.Client to override JSON marshal function.

I suggest adding these Set* functions because this way they will be available through IDEs auto-completion.

[codecov]

Codecov Report

Merging #621 (5b6825f) into master (9e2a9b7) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #621      +/-   ##
==========================================
- Coverage   95.94%   95.91%   -0.04%     
==========================================
  Files          10       10              
  Lines        1357     1395      +38     
==========================================
+ Hits         1302     1338      +36     
- Misses         34       35       +1     
- Partials       21       22       +1     

Impacted Files	Coverage Δ
client.go	97.90% <100.00%> (+0.13%)	⬆️
middleware.go	90.64% <0.00%> (-0.63%)	⬇️
retry.go	100.00% <0.00%> (ø)
request.go	95.47% <0.00%> (ø)
redirect.go	94.11% <0.00%> (ø)
response.go	100.00% <0.00%> (ø)

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[jeevatkm]

@GRbit Thanks for your PR. Your PR description put a smile on my face, thanks.

Can you please add test cases for this PR? see here for more info

[GRbit]

@jeevatkm I'm glad that it makes you smile.

Sorry for taking your time on that, but could you please tell me what kind of tests should I do? The only test I can come up with is something like this:

func TestClientJSON(t *testing.T) {
	m := func (v interface{}) ([]byte, error) { return nil,nil }
	c := New().SetJSONMarshaler(m)
	assertEqual(t, m, c.JSONMarshal)
}

But it looks silly for me to test such things because I don't think this test could possibly be helpful.

If this is what you looking for – I'll be glad to add a test for each function. If not, please show me some examples in the code

[jeevatkm]

@GRbit Thanks for the getting back.

@jeevatkm I'm glad that it makes you smile.

Sorry for taking your time on that ...

Just to be clear, why I mentioned about smile is regarding this part from the PR description. Because, time-to-time, I also do the same!

(let's be honest it's not only me who doesn't read docs)

---

I understand, what you mean. However, based on the PR context, we are introducing a new setter methods for populating certain field. So it make sense to add a tiny test case which calls those setter(s) and does the assertion.

[GRbit]

@jeevatkm I respect your standards, so my only question was "how should I make those tests?". Please check out the code I've just added, I hope it's ok.

[jeevatkm]

Thanks @GRbit for your contribution.