[feat] Fix rate limiting, add autojoin space & rooms

[benjamsf]

User-facing summary

• Fix strict rate limiting that fails on creating a space or any more rooms than 2 at a time
• Support matrixrmapi bot user that will do user crud via a secret
• Ensure incoming users join space & rooms generated by matrixrampi bot user
• Parametrize federation options, do we want an instance to be capable of federation and if so, how?

Why It's Good for the Product (Release Goal)

• Improve usability

Any Other You'd Like to Mention

• See readme at https://github.com/pvarki/docker-synapse-server/blob/fix-rate-limiting/README.md