ConvertsToJson::toJson() can return false despite its `: string` return type

[dru1x]

Summary

ConvertsToJson::toJson() calls json_encode() with no flags, so it can return false on encoding failure despite its declared : string return type. Every other JSON boundary in the codebase throws instead.

Details

src/Support/ConvertsToJson.php:24-27:

public function toJson(): string
{
    return json_encode($this);
}

json_encode() returns false on failure (e.g. malformed UTF-8 in a title/body/data field), which violates the declared : string return type. Without strict_types in this file, this doesn't fatal immediately at the call site, but it's a silent false-as-string bug waiting to surface — e.g. under strict_types=1, or in any caller that treats the result as a genuine JSON string (writing it to a file, sending it over HTTP, etc.).

By contrast:

• ConvertsFromJson::jsonDecode() (src/Support/ConvertsFromJson.php:28) uses JSON_THROW_ON_ERROR.
• SendNotificationsRequest::preventTooMuchMessageData() (src/Request/SendNotificationsRequest.php:164) uses JSON_THROW_ON_ERROR.

toJson() is the odd one out.

Suggested fix

Add the JSON_THROW_ON_ERROR flag to json_encode() in toJson(), matching the rest of the codebase's JSON-boundary handling.

Test gap

No test currently encodes a value that would fail JSON encoding (e.g. invalid UTF-8 in a message field) to confirm a JsonException is thrown rather than a silent false.