Add support for POST with json body

src/main/kotlin/org/koitharu/kotatsu/parsers/network/OkHttpWebClient.kt

@@ -61,18 +61,22 @@ class OkHttpWebClient(
 		return httpClient.newCall(request.build()).await().ensureSuccess()
 	}
 
-    override suspend fun graphQLQuery(endpoint: String, query: String): JSONObject {
-        val body = JSONObject()
-        body.put("operationName", null as Any?)
-        body.put("variables", JSONObject())
-        body.put("query", "{$query}")
+	override suspend fun httpPost(url: HttpUrl, body: JSONObject): Response {
 		val mediaType = "application/json; charset=utf-8".toMediaType()
 		val requestBody = body.toString().toRequestBody(mediaType)
 		val request = Request.Builder()
 			.post(requestBody)
-            .url(endpoint)
+			.url(url)
 			.addTags()
-        val json = httpClient.newCall(request.build()).await().ensureSuccess().parseJson()
+		return httpClient.newCall(request.build()).await().ensureSuccess()
+	}
+
+	override suspend fun graphQLQuery(endpoint: String, query: String): JSONObject {
+		val body = JSONObject()
+		body.put("operationName", null as Any?)
+		body.put("variables", JSONObject())
+		body.put("query", "{$query}")
+		val json = httpPost(endpoint, body).parseJson()
 		json.optJSONArray("errors")?.let {
 			if (it.length() != 0) {
 				throw GraphQLException(it)
@@ -82,9 +86,7 @@ class OkHttpWebClient(
 	}
 
 	private fun Request.Builder.addTags(): Request.Builder {
-        if (mangaSource != null) {
 		tag(MangaSource::class.java, mangaSource)
-        }
 		return this
 	}
 

src/main/kotlin/org/koitharu/kotatsu/parsers/network/WebClient.kt

@@ -59,6 +59,20 @@ interface WebClient {
 	 */
 	suspend fun httpPost(url: HttpUrl, payload: String): Response
 
+	/**
+	 * Do a POST http request to specific url with json payload
+	 * @param url
+	 * @param body
+	 */
+	suspend fun httpPost(url: String, body: JSONObject): Response = httpPost(url.toHttpUrl(), body)
+
+	/**
+	 * Do a POST http request to specific url with json payload
+	 * @param url
+	 * @param body
+	 */
+	suspend fun httpPost(url: HttpUrl, body: JSONObject): Response
+
 	/**
 	 * Do a GraphQL request to specific url
 	 * @param endpoint an url