Notify on bot-guild integration

For operators to do capacity planning and performance tuning, we ought to notify the dev guild when the bot is integrated with a new guild.

Details to include:

• Guild ID
• Owner ID
• Abstract guild size

Where the guild size is computed based on membership count, currently online users and the guild's membership and presence limits. For example, if a guild has a membership greater than the soft limit imposed on new guilds, we call that "huge."

Further metadata is intentionally omitted. If deemed necessary, the operator can use the inspect command for details.