Fix missing link

[nucleus-ffm]

fix #119 and fix #120

[MatsG23]

I used the chance to change the return value for an invalid phone number and email address to null. I think this should be a cleaner approach. Additionally, the extractPhoneNumber has split the contact text but if I understood it correctly we always returned the first element anyways. I adjusted it to match the logic in extractWebAddress more closely

[MatsG23]

Two further questions:

• Should we show a toast or print a log if there is no extracted value for the web address/phone number? It may appear like the app is lagging if that special extraction case ever occurs.
• Can the contact string actually contain multiple phone numbers? How to handle that case?

[nucleus-ffm]

Additionally, the extractPhoneNumber has split the contact text but if I understood it correctly we always returned the first element anyways. I adjusted it to match the logic in extractWebAddress more closely

We can not do this that way. A common case is e.g. "Bürgertelefon 1234 5678" so we have to filter the "Bürgertelefon in the front to get the telephone number. I had to change that back.

In general, the contact field is in the CAP docu defined as "The text describing the contact for follow-up and confirmation of the alert message (OPTIONAL)". So, there can be anything inside that field. I also saw an alert containing a URL inside the contact field.