FRA-2021: Escape non-ascii characters

[alanjcharles14]

Escapes any non-ASCII character in the header value to a JSON \uXXXX sequence so the value is always ASCII-safe, while remaining valid JSON that the backend decodes identically.

[alanjcharles14]

probably not strictly necessary, but fun

[lmeier]

@alanjcharles14 did we test against the server with an escaped name? Just to confirm e2e behavior? Otherwise lgtm

[alanjcharles14]

@lmeier seems unnecessary since the server is just parsing the json which is functionally equivalent to what the tests here are doing.

    let applicationInfo;
    try {
      applicationInfo = headers['x-radar-app-info'] ? JSON.parse(headers['x-radar-app-info']) : undefined;
    } catch {
      applicationInfo = undefined;
    }

running this in a terminal shows that it was handled correctly on the server already and handles the new fix though: