account types: Loosen identityOfAccount to take account-like AccountStatus

I thought the added $ReadOnly here would be unnecessary, since
Identity is a read-only object type. I guess I was wrong; if I
remove it, I get errors about specific properties on

  { ...Identity, ... }

saying they are writable.

Author: chrisbobbe

src/account/accountMisc.js

@@ -5,7 +5,7 @@ const identitySlice = ({ realm, email }): Identity => ({ realm, email });
 
 export const identityOfAuth: Auth => Identity = identitySlice;
 
-export const identityOfAccount: Account => Identity = identitySlice;
+export const identityOfAccount: ($ReadOnly<{ ...Identity, ... }>) => Identity = identitySlice;
 
 /** A string corresponding uniquely to an identity, for use in `Map`s. */
 export const keyOfIdentity = ({ realm, email }: Identity): string =>