Refractor ApiClient and add support for body params

ApiClient was refractored to use PIMPL. This is mainly done to reduce
compile times whenever the implementation of ApiClient itself changes,
since a lot of files include it.

The loaders have gained support for body parameters, this was somehow
omitted before.

core/codegen/loader_header.hbs

@@ -18,6 +18,8 @@ public:
 protected:
 	QString path(const {{e.endpoint.parameterType}}& parameters) const override;
 	QUrlQuery query(const {{e.endpoint.parameterType}}& parameters) const override;
+	QByteArray body(const {{e.endpoint.parameterType}}& parameters) const override;
+	QNetworkAccessManager::Operation operation() const override;
 };
 {{/if}}
 {{/each}}

core/codegen/loader_implementation.hbs

@@ -35,5 +35,23 @@ QUrlQuery {{e.className}}Loader::query(const {{e.endpoint.parameterType}} &param
 	return result;
 }
 
+QByteArray {{e.className}}Loader::body(const {{e.endpoint.parameterType}} &params) const {
+
+	{{#if e.endpoint.bodyParameters.length == 1}}
+	return Support::toString<{{e.endpoint.bodyParameters[0].type.typeNameWithQualifiers}}>(params.body()).toUtf8();
+
+	{{else}}
+	return QByteArray();
+
+	{{/if}}
+}
+
+QNetworkAccessManager::Operation {{e.className}}Loader::operation() const {
+	// HTTP method {{e.operation}}
+
+	return QNetworkAccessManager::{{e.operation}}Operation;
+
+}
+
 {{/if}}
 {{/each}}

core/codegen/loader_types_header.hbs

@@ -51,6 +51,18 @@ private:
 
 {{/each}}
 
+{{#if e.bodyParameters.length > 0}}
+	// Body parameters
+
+	{{#if e.bodyParameters.length == 1}}
+	{{e.bodyParameters[0].type.typeNameWithQualifiers}} m_body;
+
+	{{else}}
+	//FIXME: Multiple body options not implemented.
+
+	{{/if}}
+{{/if}}
+
 };