Don't provide 'api_id' and 'api_hash' by default.

We ask the developer to obtain his own api credentials, because
the bundled 'api_id' / 'api_hash' are strictly limited by the server.

The old credentials still could be used for test purposes,
but the developer will need to explicitly opt-in to use them.

docs/api_credentials.md

@@ -0,0 +1,13 @@
+## Obtaining your API credentials
+
+To build your version of Telegram Desktop you're required to provide your own **api_id** and **api_hash** for the Telegram API access.
+
+How to obtain your **api_id** and **api_hash** is described here: [https://core.telegram.org/api/obtaining_api_id](https://core.telegram.org/api/obtaining_api_id)
+
+If you're building the application not for deployment, but only for test purposes you can use TEST ONLY credentials, which are very limited by the Telegram API server:
+
+**api_id**: 17349
+**api_hash**: 344583e45741c457fe1862106095a5eb
+
+Your users will start getting internal server errors on login if you deploy an app using those **api_id** and **api_hash**.
+

docs/building-cmake.md

@@ -4,6 +4,10 @@
 
 Choose an empty folder for the future build, for example **/home/user/TBuild**. It will be named ***BuildPath*** in the rest of this document.
 
+### Obtain your API credentials
+
+You will require **api_id** and **api_hash** to access the Telegram API servers. To learn how to obtain them [click here][api_credentials].
+
 ### Install software and required packages
 
 You will need GCC 7.2 and CMake 3.2 installed. To install them and all the required dependencies run
@@ -150,9 +154,9 @@ Go to ***BuildPath*** and run
 
 ### Building the project
 
-Go to ***BuildPath*/tdesktop/Telegram** and run
+Go to ***BuildPath*/tdesktop/Telegram** and run (using [your **api_id** and **api_hash**](#obtain-your-api-credentials))
 
-    gyp/refresh.sh
+    gyp/refresh.sh --api-id YOUR_API_ID --api-hash YOUR_API_HASH
 
 To make Debug version go to ***BuildPath*/tdesktop/out/Debug** and run
 
@@ -164,3 +168,4 @@ To make Release version go to ***BuildPath*/tdesktop/out/Release** and run
 
 You can debug your builds from Qt Creator, just open **CMakeLists.txt** from ***BuildPath*/tdesktop/out/Debug** and launch with debug.
 
+[api_credentials]: api_credentials.md

docs/building-msvc.md

@@ -12,6 +12,10 @@ Choose an empty folder for the future build, for example **D:\\TBuild**. It will
 
 All commands (if not stated otherwise) will be launched from **x86 Native Tools Command Prompt for VS 2017.bat** (should be in **Start Menu > Visual Studio 2017** menu folder). Pay attention not to use any other Command Prompt.
 
+### Obtain your API credentials
+
+You will require **api_id** and **api_hash** to access the Telegram API servers. To learn how to obtain them [click here][api_credentials].
+
 ## Install third party software
 
 * Download **ActivePerl** installer from [https://www.activestate.com/activeperl/downloads](https://www.activestate.com/activeperl/downloads) and install to ***BuildPath*\\ThirdParty\\Perl**
@@ -170,3 +174,5 @@ For better debugging you may want to install Qt Visual Studio Tools:
 * Go to **Online** tab
 * Search for **Qt**
 * Install **Qt Visual Studio Tools** extension
+
+[api_credentials]: api_credentials.md

docs/building-xcode.md

@@ -4,6 +4,10 @@
 
 Choose a folder for the future build, for example **/Users/user/TBuild**. It will be named ***BuildPath*** in the rest of this document. All commands will be launched from Terminal.
 
+### Obtain your API credentials
+
+You will require **api_id** and **api_hash** to access the Telegram API servers. To learn how to obtain them [click here][api_credentials].
+
 ### Download libraries
 
 Download [**xz-5.0.5**](http://tukaani.org/xz/xz-5.0.5.tar.gz) and unpack to ***BuildPath*/Libraries/xz-5.0.5**
@@ -138,3 +142,5 @@ Go to ***BuildPath*/tdesktop/Telegram** and run
     gyp/refresh.sh
 
 Then launch Xcode, open ***BuildPath*/tdesktop/Telegram/Telegram.xcodeproj** and build for Debug / Release.
+
+[api_credentials]: api_credentials.md