Add message endpoint (#13)

Reviewed-on: phoenix/textsender_api#13

src/caller/mod.rs

@@ -1,4 +1,5 @@
 pub mod contact;
+pub mod message;
 
 pub mod endpoints {
     pub const ROOT: &str = "/";
@@ -9,6 +10,8 @@ pub mod endpoints {
     pub const GET_CONTACT: &str = "/api/v1/contact";
     /// Constant for updating names of a Contact endpoint
     pub const UPDATE_CONTACT_NAME: &str = "/api/v1/contact/update";
+    /// Constant for adding message endpoint
+    pub const ADD_MESSAGE: &str = "/api/v1/message/new";
 }
 
 pub mod response {