[ITS-90] /isotope-correction

[Crparedes]

Issues received by email from Dr Patrick Rourke, Chairperson of CCT-WG-Dig:

• The Nov 2024 feedback mentioned that these API calls (/calculate-equilibrium-hydrogen /neon, /oxygen-17 and /oxygen-18) should probably consider degrees of freedom, but can't tell if this has been implemented. What do we expect here? Can we give more guidance to the BIPM?
• The API calls (/neon, /oxygen-17 and /oxygen-18) now give uncertainties that are much closer to what Peter submitted for his Nov 2024 test cases. But they are not exactly the same. What is the source of the differences?
• All isotope-correction calls (/calculate-equilibrium-hydrogen /neon, /oxygen-17 and /oxygen-18) in the ITS-90 API should provide weblinks to the relevant documents in the description and also in the returned data for each function call.
  • https://www.bipm.org/documents/20126/41791796/MeP_K_Technical_Annex.pdf