[TF] put api keys in separate file

This makes it easier to manage them as the don't need to be weirdly
quoted.
And they are now .gitignored so accidentally committing them should be
harder.

.gitignore

@@ -11,3 +11,4 @@ TMessagesProj/.externalNativeBuild/
 TMessagesProj/libs
 3rdParty/download
 3rdParty/unpacked
+API_KEYS

README.md

@@ -74,11 +74,11 @@ MTproto protocol manuals: https://core.telegram.org/mtproto
       ```
 
 4. If you want to publish a modified version of Telegram:
-      - You should get **your own API key** here: https://core.telegram.org/api/obtaining_api_id and update the file `TMessagesProj/build.gradle` accordingly.
-        Something like this will work, note the double quoting of the APP_HASH value:
+      - You should get **your own API key** here: https://core.telegram.org/api/obtaining_api_id and create a file called `API_KEYS` in the root source directory.
+        The contents should look something like this:
         ```
-        buildConfigField 'int', 'APP_ID', "12345"
-        buildConfigField 'String', 'APP_HASH', '"aaaaaaaabbbbbbccccccfffffff001122"'
+        APP_ID = 12345
+        APP_HASH = aaaaaaaabbbbbbccccccfffffff001122
         ```
       - Do not use the name Telegram and the standard logo (white paper plane in a blue circle) for your app — or make sure your users understand that it is unofficial
       - Take good care of your users' data and privacy

TMessagesProj/build.gradle

@@ -19,6 +19,18 @@ dependencies {
     implementation 'org.osmdroid:osmdroid-android:5.6.5'
 }
 
+//return an api key from a properties file.
+def getAppId(){
+    Properties properties = new Properties()
+    properties.load(new FileInputStream("./API_KEYS"))
+    return properties.get("APP_ID")
+}
+def getAppHash(){
+    Properties properties = new Properties()
+    properties.load(new FileInputStream("./API_KEYS"))
+    return "\"" + properties.get("APP_HASH") + "\""
+}
+
 android {
     compileSdkVersion 25
 
@@ -144,8 +156,8 @@ android {
         versionName "4.2.1"
 
         //obtain your own keys at https://core.telegram.org/api/obtaining_api_id
-        buildConfigField 'int', 'APP_ID', AppId
-        buildConfigField 'String', 'APP_HASH', AppHash
+        buildConfigField 'int', 'APP_ID', getAppId()
+        buildConfigField 'String', 'APP_HASH', getAppHash()
 
         externalNativeBuild {
             ndkBuild {