Support for multipart/form-data

[davidebeatrici]

vgram/types.v

Lines 805 to 806 in 32429ae

	// media File to send. Pass a file_id to send a file that exists on the Telegram servers (recommended), pass an HTTP URL for Telegram to get a file from the Internet, or pass “attach://” to upload a new one using multipart/form-data under name. More info on Sending Files »
	media string

From https://core.telegram.org/bots/api#sending-files:

Sending files

There are three ways to send files (photos, stickers, audio, media, etc.):

1. If the file is already stored somewhere on the Telegram servers, you don't need to reupload it: each file object has a file_id field, simply pass this file_id as a parameter instead of uploading. There are no limits for files sent this way.
2. Provide Telegram with an HTTP URL for the file to be sent. Telegram will download and send the file. 5 MB max size for photos and 20 MB max for other types of content.
3. Post the file using multipart/form-data in the usual way that files are uploaded via the browser. 10 MB max size for photos, 50 MB for other files.

[davidebeatrici]

For reference, here's how a Lua library does it: https://github.com/wrxck/telegram-bot-lua/blob/9fe54d9ea25621a7de8f40518cf3b63d3e3d08e9/src/core.lua#L40-L93

We could use net.http.FileData and eventually net.http.post_multipart_form().

[dariotarantini]

I would like to wait until dev branch works with V lang. After that, I will implement this

[davidebeatrici]

Sounds good, thanks!