[GDPR] Data Consent

• As a Releng Team Member,
• I want to configure consent to all legal part(privacy policy, code of conduct, ...)
• so that:

• Define and configure synapse agreement (https://matrix-org.github.io/synapse/latest/consent_tracking.html#collecting-policy-agreement-from-a-user)
• Server notice
• create html form to collect agreement with consent
• Create a specific appservice for federated users