added a builder pattern to CorsOptions (#75)

* added a builder pattern to CorsOptions

* builder pattern in corsOptions is now consuming

src/lib.rs

@@ -1152,6 +1152,60 @@ impl CorsOptions {
     pub fn to_cors(&self) -> Result<Cors, Error> {
         Cors::from_options(self)
     }
+
+    /// Sets the allowed origins
+    pub fn allowed_origins(mut self, allowed_origins: AllowedOrigins) -> Self {
+        self.allowed_origins = allowed_origins;
+        self
+    }
+
+    /// Sets the allowed methodes
+    pub fn allowed_methods(mut self, allowed_methods: AllowedMethods) -> Self {
+        self.allowed_methods = allowed_methods;
+        self
+    }
+
+    /// Sets the allowed headers
+    pub fn allowed_headers(mut self, allowed_headers: AllowedHeaders) -> Self {
+        self.allowed_headers = allowed_headers;
+        self
+    }
+
+    /// Marks if credentials are allowed
+    pub fn allow_credentials(mut self, allow_credentials: bool) -> Self {
+        self.allow_credentials = allow_credentials;
+        self
+    }
+
+    /// Sets the expose headers
+    pub fn expose_headers(mut self, expose_headers: HashSet<String>) -> Self {
+        self.expose_headers = expose_headers;
+        self
+    }
+
+    /// Sets the max age
+    pub fn max_age(mut self, max_age: Option<usize>) -> Self {
+        self.max_age = max_age;
+        self
+    }
+
+    /// Marks if wildcards are send
+    pub fn send_wildcard(mut self, send_wildcard: bool) -> Self {
+        self.send_wildcard = send_wildcard;
+        self
+    }
+
+    /// Sets the base of the fairing route
+    pub fn fairing_route_base<S: Into<String>>(mut self, fairing_route_base: S) -> Self {
+        self.fairing_route_base = fairing_route_base.into();
+        self
+    }
+
+    /// Sets the rank of the fairing route
+    pub fn fairing_route_rank(mut self, fairing_route_rank: isize) ->  Self {
+        self.fairing_route_rank = fairing_route_rank;
+        self
+    }
 }
 
 /// Response generator and [Fairing](https://rocket.rs/guide/fairings/) for CORS
@@ -2025,6 +2079,18 @@ mod tests {
         cors.validate().unwrap();
     }
 
+    #[test]
+    fn cors_options_from_builder_pattern() {
+        let allowed_origins = AllowedOrigins::some_exact(&["https://www.acme.com"]);
+        let cors_options_from_builder = CorsOptions::default()
+            .allowed_origins(allowed_origins)
+            .allowed_methods(vec![http::Method::Get].into_iter().map(From::from).collect())
+            .allowed_headers(AllowedHeaders::some(&[&"Authorization", "Accept"]))
+            .allow_credentials(true)
+            .expose_headers(["Content-Type", "X-Custom"].iter().map(|s| (*s).to_string()).collect());
+        assert_eq!(cors_options_from_builder, make_cors_options());
+    }
+
     /// Check that the the default deserialization matches the one returned by `Default::default`
     #[cfg(feature = "serialization")]
     #[test]