Update terms of service and/ or monarch-link app for user data timeout

[VenissaCarolQuadros]

We need to update the terms of service and/ or monarch-link-app for user data timeout. The data includes:

1. The code the Monarchs are subscribed to and the associated secret key (generated by the server)
2. The SVG data published by the user and the user-readable channel title

We need to decide on:

1. How long each of the components of this data is stored
2. Whether or not the user can force a particular code if it has been erased from the server store (for now: Yes! Unless there is a very strong reason not to)
3. How we handle scenarios where the code a user wants to use (2.) is already assigned to another user

[VenissaCarolQuadros]

Recommended changes to terms of service:

• The Overview of the IMAGE Extension in the web store needs to be modified to reflect that we now support Monarch and that you will be able to view automatically generated, partially or completely customized experiences on it using the authoring tool. (Refer "allowed use")
• Currently any data shared between the Extension, TAT and monarch-link-app is encrypted using AES-CBC. We do not explicitly describe the data flow in our current terms but I believe we meet this condition with our current setup -> Extensions must transmit "personal and sensitive user data" over a secure connection (e.g. HTTPS, WSS) and stored at rest using a strong encryption method such as RSA or AES.
• We do not have any explicit terms on user data timeout. However, to avoid storing unused data indefinitely on our server a cron job has been setup to delete entries that haven't been updated in the last hour (Save source graphic in monarch-link-app and clear unused entries periodically #927).

Handling user data timeout:

• Currently, the user can force a particular share code if it has been erased from the server store. In the off chance that this code is already assigned to another user (chance is 1/262144), 401 is returned. This might need to be revisited when this is no longer just a prototype!