High Sierra Peer-to-Peer sync and App Transport Security

First comment:

copied from cbl-ios #1936

For customers who have upgraded to High Sierra, I was getting reports of SSL connection errors when they were attempting to use peer-to-peer syncing. With the most recent High Sierra fix for the untrustworthy SSL certificate, it was also necessary to enable the `Allow Arbitrary Loads YES` option in the `Info.plist` file for the `App Transport Security` section on macOS to avoid this error. I thought I'd file this issue so you can update the Wiki to note this change in requirement with High Sierra.

This was the output in the log without `Allow Arbitrary Loads YES` enabled:

```
default 08:36:41.442048 +0100 Tap Forms Mac 5 System Trust Evaluation yielded status(-9802)
error 08:36:41.442077 +0100 Tap Forms Mac 5 ATS failed system trust
error 08:36:41.442132 +0100 Tap Forms Mac 5 System Trust failed for [9:0x604000572b40]
default 08:36:41.442165 +0100 Tap Forms Mac 5 TIC TLS Trust Result [9:0x604000572b40]: 4
error 08:36:41.442206 +0100 Tap Forms Mac 5 TIC SSL Trust Error [9:0x604000572b40]: 3:0
default 08:36:41.442243 +0100 Tap Forms Mac 5 TIC TCP Conn Cancel [9:0x604000572b40]
default 08:36:41.442390 +0100 Tap Forms Mac 5 NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9802)
error 08:36:41.442474 +0100 Tap Forms Mac 5 Task <E5BF0E23-E22A-4046-A0DC-87E3EEC36C5E>.<1> HTTP load failed (error code: -1200 [3:-9802])
error 08:36:41.442599 +0100 Tap Forms Mac 5 Task <E5BF0E23-E22A-4046-A0DC-87E3EEC36C5E>.<1> finished with error - code: -1200
default 08:36:41.443258 +0100 Tap Forms Mac 5 TIC TCP Conn Destroyed [9:0x604000572b40]
```

Afterwards there were no errors and an SSL connection was established.

--------

• Version: 1.4.1
• Client OS: macOS High Sierra
• Server: peer-to-peer

see other comments: https://github.com/couchbaselabs/couchbase-mobile-portal/issues/826