fix(model, http)!: fix role position update payload and allow audit log reason

[suneettipirneni]

Closes #2338 and adds audit log reason support for this endpoint.

[vilgotf]

(Thinking out loud) We could keep the &[(Id, u64)] parameter as is, with a little magic, via a custom serializer (on a private newtype) like:

-     roles: &'a [(Id<RoleMarker>, u64)],
+     roles: Roles<'a>,

struct Roles<'a>(&'a [(Id<RoleMarker>, u64)]);

impl Serialize for Roles<'_> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        serializer.collect_seq(self.0.map(/* tuple to RolePosition  */))
    }
}

[Erk-]

I think I would like the struct way more than the tuple.

[AEnterprise]

Not a huge fan of the "RolePosition" name since it contains more then just the position. Maybe "RoleMeta" or so might be better but that might then also implies it has more? not entirely sure if there is a better name