putUrl method
Add a URL attribute for the given key.
The attribute key should be a string composed of letters, numbers or underscores ([a-z0-9_]) and can't be longer than 30 characters.
While the value is an Uri instance, it must be a valid URL and not be longer than 2048 characters.
Implementation
BatchEventAttributes putUrl(String key, Uri value) {
_attributes[key.toLowerCase()] = TypedAttribute(type: TypedAttributeType.url, value: value.toString());
return this;
}