fix(http): correctly set content type for POST requests

lib/api/lidarr/api.dart

@@ -21,6 +21,8 @@ abstract class LidarrAPI {
       queryParameters: {
         if (apiKey.isNotEmpty) 'apikey': apiKey,
       },
+      contentType: Headers.jsonContentType,
+      responseType: ResponseType.json,
     ));
     return _LidarrAPI(dio, baseUrl: _baseUrl(host));
   }

lib/api/nzbget/api.dart

@@ -1,8 +1,6 @@
-import 'dart:convert';
-import 'package:dio/dio.dart';
 import 'package:lunasea/api/nzbget/models/status.dart';
 import 'package:lunasea/api/nzbget/models/version.dart';
-import 'package:retrofit/retrofit.dart';
+import 'package:lunasea/vendor.dart';
 
 part 'api.g.dart';
 
@@ -51,6 +49,8 @@ abstract class NZBGetAPI {
       headers: headers,
       followRedirects: true,
       maxRedirects: 5,
+      contentType: Headers.jsonContentType,
+      responseType: ResponseType.json,
     ));
     _attachInterceptor(dio);
     _setResponseTransformer(dio);

lib/api/overseerr/api.dart

@@ -27,6 +27,8 @@ abstract class OverseerrAPI {
           'X-Api-Key': apiKey,
           ...headers,
         },
+        contentType: Headers.jsonContentType,
+        responseType: ResponseType.json,
         followRedirects: true,
         maxRedirects: 5,
       ),

lib/api/radarr/radarr.dart

@@ -68,6 +68,7 @@ class RadarrAPI {
         headers: headers,
         followRedirects: followRedirects,
         maxRedirects: maxRedirects,
+        contentType: Headers.jsonContentType,
         responseType: ResponseType.json,
       ),
     );

lib/api/sabnzbd/api.dart

@@ -32,6 +32,8 @@ abstract class SABnzbdAPI {
       headers: headers,
       followRedirects: true,
       maxRedirects: 5,
+      contentType: Headers.jsonContentType,
+      responseType: ResponseType.json,
       queryParameters: {
         if (apiKey.isNotEmpty) 'apikey': apiKey,
         'output': 'json',

lib/api/sonarr/sonarr.dart

@@ -36,6 +36,7 @@ class SonarrAPI {
         queryParameters: {
           'apikey': apiKey,
         },
+        contentType: Headers.jsonContentType,
         responseType: ResponseType.json,
         headers: headers,
         followRedirects: followRedirects,

lib/api/tautulli/tautulli.dart

@@ -51,6 +51,7 @@ class TautulliAPI {
         queryParameters: {
           'apikey': apiKey,
         },
+        contentType: Headers.jsonContentType,
         responseType: ResponseType.json,
         headers: headers,
         followRedirects: followRedirects,