Implementing a "pets finder" application

The previous recipe showed us how a map can be used to display live information, updated at a relatively high frequency, in a scenario where the user is passive in practice and just observes what a server is broadcasting. In this recipe, we want to explore a much more interactive scenario, where the information displayed on the map is provided by the users.

This application can be used to place the name and a picture of a pet that has been lost on a map. These details will be added to other users' maps in real time. Anybody observing the map could drag-and-drop any marker on a different position to notify that the pet was there. Finally, the user who first raised an alarm about a specific lost pet can declare that he/she found it, and this action will correspond to the removal of the markers related to that specific animal from all the connected maps. This is illustrated in the following screenshot:

From a SignalR's perspective, we'll use the following...