Alpine unable to install local .apk file

Install Temurin following Instructions on the [website](https://adoptium.net/installation/linux/) for Alpine Linux.

`apk add` works fine
```
/ # apk add temurin-17-jdk
(1/8) Installing java-common (0.5-r0)
(2/8) Installing libffi (3.4.4-r2)
(3/8) Installing p11-kit (0.24.1-r2)
(4/8) Installing libtasn1 (4.19.0-r1)
(5/8) Installing p11-kit-trust (0.24.1-r2)
(6/8) Installing ca-certificates (20230506-r0)
(7/8) Installing java-cacerts (1.0-r1)
(8/8) Installing temurin-17-jdk (17.0.7_p7-r0)
Executing busybox-1.36.1-r0.trigger
Executing java-common-0.5-r0.trigger
Executing ca-certificates-20230506-r0.trigger
OK: 270 MiB in 23 packages
```

But it doesn't work if I download the .apk file to the local directory and install it
```
~ # apk fetch temurin-17-jdk
Downloading temurin-17-jdk-17.0.7_p7-r0
~ # ls
temurin-17-jdk-17.0.7_p7-r0.apk
~ # apk add temurin-17-jdk-17.0.7_p7-r0.apk
ERROR: temurin-17-jdk-17.0.7_p7-r0.apk: UNTRUSTED signature
```

It looks like the .apk file can't be verified
```
~ # apk verify temurin-17-jdk-17.0.7_p7-r0.apk
temurin-17-jdk-17.0.7_p7-r0.apk: 0 - UNTRUSTED
```

Reproduce the Alpine Linux commands from the issue, including apk fetch, apk add, and apk verify for the downloaded Temurin package. Investigate the local package signature failure; done means a locally downloaded .apk can be verified and installed successfully on Alpine Linux.

Written by the indexing model from the issue text.