the access to Config elements is internal now, add this to migration guide

[milyin]

Describe the release item

From @kydos

the following code does not compile:

fn main() {
    let mut c = zenoh::Config::default();
    c.set_mode(zenoh::config::WhatAmI::Client);
}

Found the issue, in 1.0.0 these APIs are internal and need to be activated via:
zenoh = { version = "1.0.0", features = ["internal", "internal_config"] }
We should have this on the Migration Guide.

[Mallets]

The API is marked as internal, so I'm not sure it should be covered in the migration guide.
IMHO it would be better to use insert_json5 API also in our examples and eventually adding a dedicated examples showing how to programmatically configuring zenoh.

[samcarey]

it would be better to use insert_json5

Why is insert_json5 being promoted for manipulating a Rust struct?
Why not use setter methods for the individual fields, so the inserted fields and values are type-checked at compile time instead of being parsed from strings at runtime?