refactor: explicate intent on make_payment_request interface

[blaggacao]

Next part of #40845

cc @ruthra-kumar

[blaggacao]

You may say Im a dreamer, but Im not the only one, I hope someday you will join us, and the world will live as one. - John Lennon

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_{Kindly help move this PR forward. Many thanks from Yours Sincerely!}

[blaggacao]

I have just three things to teach: simplicity, patience, compassion. These three are your greatest treasures. - Lao Tzu

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_{Kindly help move this PR forward. Many thanks from Yours Sincerely!}

[blaggacao]

@ruthra-kumar I hope all is well and work not too inundating. Didn't we want to advance on this on some sort of cadence? This is also the last one of the previous refactorings to accommodate the new gatweawy api (which I will restructure in its commit sequence after this). This here is lightwight and - I hope - easy to review. All in all good for an easy "cross-of-the-list reward".