Building strings based on dataset elements

Sometimes, we face the problem of generating text based on collections' elements. This is where the Iterable.joinToString() extension function can help. For example, we can consider working on an email-message-forwarding feature. When a user clicks the forward button, the original message's body text is concatenated, with the prefix looking something like this:

<br/>
<p>---------- Forwarded message ----------</p>
<p>
From: [e-mail] <br/>
Date: 14/04/2000 <br/>
Subject: Any plans for the evening?<br/>
To: [e-mail], [e-mail]<br/>
</p>

In this recipe, we are going to implement a function that is going to generate the recipients' string, for example:

To: [e-mail], [e-mail]</br>

For a given list of Address type objects, it is defined...