Visual clue for linked cards/boards on card

Describe the solution you'd like
I am using the project relationships quite extensively in Deck and have found it would be useful if there was some kind of visual clue on the card to show that 1) the card is related to another card/board, and 2) the relationship count.

It could be similar to the list item counts.

Describe alternatives you've considered
AFAIK, the only alternative is to open each card and manually view the links.

Additional context

For a few of my bigger projects, I create an overview board... this board contains my main goals (as cards on the board). For each of the cards, I will link to other boards and cards (from other boards). You can look at it as the 10,000 ft. view, while the linked boards are the ground level detail.

So imagine that there are multiple cards from multiple boards related to a single goal (a card on the 'overview' board). Having the count would be useful. Essentially turning the overview board as a kind of report board.

In general, are there any plans to improve the relationship UI?

Related to: #2238

No files, tests, or entry points are named. Start by reviewing Deck's existing card and board relationship UI and the related issue #2238; the work is complete when cards visibly indicate linked cards or boards and show their relationship count.