add serializer and deserializer as client arguments

[os-esh]

No description provided.

[github-actions]

Pull Request Test Coverage Report for Build 6508279793

• 6 of 6 (100.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 93.143%

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Files with Coverage Reduction	New Missed Lines	%
src/elastic_transport/client.jl	1	92.94%

Totals
Change from base Build 6015678386:	-0.2%
Covered Lines:	489
Relevant Lines:	525

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 6508279793

• 6 of 6 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.333%

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Totals
Change from base Build 6015678386:	0.0%
Covered Lines:	490
Relevant Lines:	525

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💛 - Coveralls