Further suggestions

Message limits:

• MAX_MESSAGES_PER_SECOND = 30
• MAX_MESSAGES_PER_SECOND_PER_CHAT = 1
• MAX_MESSAGES_PER_MINUTE_PER_GROUP = 20

File sizes

• MAX_FILESIZE_UPLOAD = 50000000 (50MB)
• MAX_FILESIZE_DOWNLOAD = 20000000 (20MB)
• There may be a special limit (size or length) for voice messages, I'll check that out

Others:

• SUPPORTED_WEBHOOK_PORTS = [443, 80, 88, 8443]

Edit: Testing these could be difficult

Looks good to me!
Tests run and are green.

MAX_MESSAGES_PER_SECOND_PER_CHAT = 1

From where was this? My bot can send me 30 messages per second.

@rahiel from the bot FAQ:

When sending messages inside a particular chat, avoid sending more than one message per second. We may allow short bursts that go over this limit, but eventually you'll begin receiving 429 errors.