@SendGridOutput ignores personalizations->dynamic_template_data

Hello.

We are trying to use SendGridOutput to send outbound emails from our functions. For each email we need to use dynamic template with handlebars. Learn more on these here:

1. https://sendgrid.com/docs/ui/sending-email/how-to-send-an-email-with-dynamic-transactional-templates/
2. https://sendgrid.com/docs/for-developers/sending-email/using-handlebars/

We've created several dynamic templates and for all of them we see similar issue: the dynamic_template_data is not being applied to the template so all placeholders are empty.

Here is the real example:

**Template code:**
```

Hello {{ firstName }}.

We've received new call back request {{ callbackId }} at {{ callbackTimestamp }}.

Please follow up with the new enrollee {{ enrolleeFirstName }} {{ enrolleeLastName }} at {{ enrolleePhone }} .

Yours truly, subscription bot.

**The value we put into the output value (OutputBinding outSendgridMessage):**
```
{
"personalizations":
[
{
"to": [{"email":"my@email.com"}],
"dynamic_template_data: {
"firstName":"Coach",
"enrolleePhone":"7879090099",
"callbackId":null,
"enrolleeFirstName":"Joe",
"enrolleeLastName":"Test105",
"callbackTimestamp":1615493135111
}
}
],
"content":[{"type":"text/html","value":"The new call back request has been received."}],
"template_id":"d-7a92d5731fc942bb87dd4bfc2ac02afd"
}
```

**The email comes without data:**

Please investigate why it is happening.

Non viene indicato alcun file o test. Inizia tracciando il binding Java @SendGridOutput con il JSON di personalizations e dynamic_template_data fornito, quindi confronta la richiesta SendGrid generata con il formato documentato. Il lavoro è completato quando il template dinamico riceve i valori di personalizzazione e li rende nell’e-mail.

Scritto dal modello di indicizzazione a partire dal testo della issue.