Exclude using of user_id in urls. Use encoded_username instead.

We sould not use user id in URLs, user name should be used instead.

User name, however, may contain some characters prohibited for use in URLs.
As a workaround, user names may be encoded with URLEncoder. To reduce code logic payload it's preferrable to introduce aditional column 'username_encoded' in the user table. username_encoded shoud be calculated during the user registation and used later in URL building.