Add a DM tool with config to encrypt DM or not and allow cold dm or not

[marc-aurele-besner]

We should add a tool for the agent to interact directly using DM

For this purposes, a few tools and config could be use

Tools

• Tools to fetch your DM (especially unread one)
• Tools to reply to DM
• Tools to send new DM (to new user)

Config

• Config to turn on/off the use of DM
• Config to turn on/off the cold DM (allowing or not the agent to send unsolicitated DM's)
• Config to turn on/off encryption for DM

I could imagine wanting to keep general experience public but encrypt dm, for example a customer support agents could receive what could be consider personal data over dm and so wanting them encrypted, while still keeping the public tweet experience public