forcing multipart overrides headers

Author: ryber

unirest/src/main/java/kong/unirest/Headers.java

@@ -73,7 +73,11 @@ public void replace(String name, String value) {
         add(name, value);
     }
 
-    private void remove(String name) {
+    /**
+     * Remove a header
+     * @param name the header name to remove
+     */
+    public void remove(String name) {
         headers.removeIf(h -> isName(h, name));
     }
 

unirest/src/main/java/kong/unirest/HttpRequestMultiPart.java

@@ -201,6 +201,7 @@ public ProgressMonitor getMonitor() {
 
     MultipartBody forceMultiPart(boolean value) {
         forceMulti = value;
+        headers.remove("Content-Type");
         return this;
     }
 }

unirest/src/test/java/BehaviorTests/MultiPartFormPostingTest.java

@@ -56,6 +56,24 @@ void overridingContentType(){
                 .assertHeader("Content-Type", "multipart/form-data");
     }
 
+    @Test
+    void overridingForcingMultiTypeOverridesHeader(){
+        Unirest.config().setDefaultHeader("Accept", "application/json")
+                .setDefaultHeader("Content-Type", "application/json")
+                .setDefaultHeader("Authorization", "Bearer xxx-abc-123");
+
+        Unirest.post(MockServer.POST)
+                .basicAuth("username", "password")
+                .multiPartContent()
+                .field("username", "xxx")
+                .field("token", "abc")
+                .field("grant_type", "password")
+                .asObject(RequestCapture.class)
+                .getBody()
+                .assertHeaderSize("Content-Type", 1)
+                .assertMultiPartContentType();
+    }
+
     @Test
     void testMultipart() throws Exception {
         Unirest.post(MockServer.POST)