Schedule message (#15)

Reviewed-on: phoenix/textsender_api#15

src/caller/mod.rs

@@ -14,6 +14,8 @@ pub mod endpoints {
     pub const ADD_MESSAGE: &str = "/api/v1/message/new";
     /// Constant for getting messages endpoint
     pub const GET_MESSAGE: &str = "/api/v1/message";
+    /// Constant for scheduling message endpoint
+    pub const SCHEDULE_MESSAGE: &str = "/api/v1/schedule/message";
 }
 
 pub mod response {