[Mainlining] Update `account_validity` requests

[odelcroi]

During the mainlining of synapse, a new optional module has been introduced to handle the account validity. This involves a new path for the account_validity requests: /_matrix/client/unstable/account_validity/ is replaced by /_synapse/client/email_account_validity/ The request format does not change

For the moment the new module has not been deployed

This path is used client side to request a new email or submit a token (send_mail and renew) - See AccountValidityAPI I don't think we are using the /renew API

1- Check the occurrences of the AccountValidityAPI use 2- Sync with Ops to set up the account_validity module on DEV platform 3- Update the service to use/test the new path on DEV platform 4- Sync with the Web, Mobile and Ops teams to define a plan to update Tchap clients and the Prod/Preprod infra

[estellecomment]

Could we

• set up a redirect from the old path to the new path
• implement the change in backend
• implement it on frontends
• remove the redirect

[giomfo]

implement the change in backend

For the second point, you mean "deploy account_validity module server side"? (This is already implemented in backend)

[odelcroi]

removing P1 as it might not be needed for mainlining