Allow only valence accounts to register to a service?

[Art3miX]

Currently anyone can register to any service, not only valence accounts.

To use a service without any errors, you need 2 requirements:

1. to be a contract
2. Implement specific messages that a service might execute on the account.

We can do a very basic verification when user tries to register to a service, we can create a simple query on valence account "IsValenceAccount", if that query fails, it means its 100% not a valence account.

But if it passes, it means either:

1. its a valence account
2. its a contract that implement this query for some reason (probably a malicious reason)

I think its a good enough way to do a simple verification, to avoid innocent mistakes, like registering a wallet to rebalancer without creating valence account first.

[Art3miX]

One extra way of doing it better, is by whitelisting code ids, and checking if the sender has valence account code id or not, this checks 2 things:

1. Its a contract, because it has a code id.
2. Its valence account, because its a whitelisted code id.

This code id check can be expended into checking whitelisted contracts in general in the future, for example if we want to verify its a valid auction contract, we can check against it, or verify services managers of other companies, etc.