Expose 3PID request fields

[portaloffreedom]

Mandatory fields are now exposed, make it impossible to send RequestTokenTo3PIDEmailJob and RequestTokenTo3PIDMSISDNJob

[KitsuneRal]

Which actual problem are you trying to solve? The proposed changes don't change anything. From the respective page at cppreference.com:

If access-specifier is omitted, it defaults to public for classes declared with class-key struct and to private for classes declared with class-key class.

[portaloffreedom]

ah! you are right, I was too quick on this. I was trying to do this:

    Quotient::EmailValidationData req {
         .email = email
    };

because I like the compact style. Today I learned two things:

• struct inherit publicly by default and
• that the compact named initialization does not work with inheritance.

[KitsuneRal]

Yeah, I was suspecting you tried to use designated initialisers with those structures. It is terribly aggravating that they let this use case fall through the C++ standard cracks.