Support unit conversion

[chargio]

User Story

As a user, I want to be able to use any unit to define my rates, so that I can use the measures that are more consistent with the tariff.

Impacts

API, UI, Docs

Role

User

Assumptions

• Binary, Si and time units are supported.

UI Details

An API call will return the list of prefixes, the list of possible units, and the combination Another API call will return the converstion

Acceptance Criteria

• [ ] It is possible to convert between any two prefixes, and between SI and binary prefixes
• [ ] When there is no possible conversion, the result is 0