allow used added CAs

src/main/AndroidManifest.xml

@@ -67,6 +67,7 @@
         android:label="@string/app_name"
         android:fullBackupContent="@xml/backup_config"
         android:theme="@style/Theme.ownCloud.Toolbar"
+        android:networkSecurityConfig="@xml/network_security_config"
         android:manageSpaceActivity="com.owncloud.android.ui.activity.ManageSpaceActivity">
         <activity
             android:name=".ui.activity.FileDisplayActivity"

src/main/res/xml/network_security_config.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<network-security-config>
+    <base-config cleartextTrafficPermitted="true">
+        <trust-anchors>
+            <!-- Trust preinstalled CAs -->
+            <certificates src="system"/>
+            <!-- Additionally trust user added CAs -->
+            <certificates src="user"/>
+        </trust-anchors>
+    </base-config>
+</network-security-config>