Add validation of generation and metageneration to upload functions

[HollayHorvath]

• An issue was already open for this problem, linked below
• Ensure the tests and linter pass
• Code coverage does not decrease - I'm not quite sure about this
• Appropriate docs were updated - I have updated the comments by adding the new parameters, if there are other places to update please let me know

Fixes #16 🦕

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[HollayHorvath]

@googlebot I signed it!

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[frankyn]

I have one nit, but overall LGTM, thanks for picking this up @HollayHorvath!

[frankyn]

Could you update the name with expected prefix of if_ to follow the API spec?

[frankyn]

One more request, could you add system tests that exercise these new parameters?

[frankyn]

Thanks for your support @HollayHorvath, you helped get this ball moving and will have it out in the library soon.

@IlyaFaer is taking the work you've done and making necessary changes to get into the library. I'm closing out this PR and continuing the remaining discussions in #111.