Add comprehensive unit tests for lib package with 91.9% coverage

[Copilot]

Adds unit tests for the lib package to achieve >90% statement coverage using only standard library testing.

Test files added

• lib_test.go - Constants, types, IgnoreIPv4/IgnoreIPv6 functions
• error_test.go - Error variable definitions
• entry_test.go - Entry struct: AddPrefix/RemovePrefix with all input types (string, net.IP, netip.Addr, netip.Prefix, pointers), IPv4-mapped IPv6, comment handling, marshal methods
• container_test.go - Container interface: CRUD operations, Lookup for IPs/CIDRs, IgnoreIP options
• config_test.go - Config registration, JSON unmarshaling for input/output converters
• converter_test.go - Converter registration and listing
• common_test.go - GetRemoteURLContent/GetRemoteURLReader with mock HTTP servers, WantedListExtended unmarshaling
• instance_test.go - Instance lifecycle: config init (local/remote), run with success/error paths

Coverage

$ go test ./lib/... -cover
ok  github.com/Loyalsoldier/geoip/lib  0.029s  coverage: 91.9% of statements

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• invalid-url-that-does-not-exist.local
  • Triggering command: /tmp/go-build901520468/b001/lib.test /tmp/go-build901520468/b001/lib.test -test.testlogfile=/tmp/go-build901520468/b001/testlog.txt -test.paniconexit0 -test.gocoverdir=/tmp/go-build901520468/b001/gocoverdir -test.timeout=10m0s -test.v=true (dns block)
  • Triggering command: /tmp/go-build3061144322/b001/lib.test /tmp/go-build3061144322/b001/lib.test -test.testlogfile=/tmp/go-build3061144322/b001/testlog.txt -test.paniconexit0 -test.gocoverdir=/tmp/go-build3061144322/b001/gocoverdir -test.timeout=10m0s -test.v=true (dns block)
  • Triggering command: /tmp/go-build3934940046/b001/lib.test /tmp/go-build3934940046/b001/lib.test -test.testlogfile=/tmp/go-build3934940046/b001/testlog.txt -test.paniconexit0 -test.gocoverdir=/tmp/go-build3934940046/b001/gocoverdir -test.timeout=10m0s -c=4 -nolocalimports -importcfg /tmp/go-build901520468/b069/importcfg -pack /opt/hostedtoolcache/go/1.24.11/x64/src/runtime/trace/annotation.go /opt/hostedtoolcache/go/1.24.11/x64/src/runtime/trace/trace.go (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Please write comprehensive unit tests for lib package and make sure the coverage rate is above 90%. Try not to use third-party Golang dependencies if possible.

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