Function add_role 

pub async fn add_role(
    client: &Client,
    token: &str,
    guild_id: &str,
    user_id: &str,
    role_id: &str,
) -> Result<(), Box<dyn Error>>

Adds a role to a user in a Discord guild.

Arguments

• client - The HTTP client used to send the request.
• token - The bot token for authentication.
• guild_id - The ID of the guild.
• user_id - The ID of the user to add the role to.
• role_id - The ID of the role to add.

Returns

A result indicating success or failure.