Now that the regex in D10388 (previous diff) can support ENS names in @ mentions, we need to make some modifications to createMemberMapForUserMentions since it constructs a member map that is used to bold mentions.
For example, since the map will link a username (john) to a user ID (92019), when we type @john, we associate it to the user ID.
For ENS names, we want to do the same. We want to have both the wallet address and the resolved ENS name mapping to the same user ID, so we attempt to insert both.
This way, for a ENS user whose name is jack.eth, the members map will have two entries mapping to the same user ID value.
Depends on D10388