Modify ExecuteMsg

Let's create messages for the two tasks of Creating a Poll and Voting on a Poll.

1. So let's open src/msg.rs and take a look at ExecuteMsg. It should look pretty empty:

#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, JsonSchema)]
#[serde(rename_all = "snake_case")]
pub enum ExecuteMsg {
    CustomMsg { val: String },
}

1. Create Poll - Let's add the following:

#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, JsonSchema)]
#[serde(rename_all = "snake_case")]
pub enum ExecuteMsg {
    CreatePoll {
        poll_id: String, 
        question: String,
        options: Vec<String>,
    }
}

2. Voting on a Poll

#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, JsonSchema)]
#[serde(rename_all = "snake_case")]
pub enum ExecuteMsg {
    CreatePoll {
        poll_id: String,
        question: String,
        options: Vec<String>,
    },
    Vote {
        poll_id: String,
        vote: String,
    },
}