caddyconfig: add global option for configuring loggers (#4028)

This change is aimed at enhancing the logging module within the
Caddyfile directive to allow users to configure logs other than the HTTP
access log stream, which is the current capability of the Caddyfile [1].
The intent here is to leverage the same syntax as the server log
directive at a global level, so that similar customizations can be added
without needing to resort to a JSON-based configuration.

Discussion for this approach happened in the referenced issue.

Closes https://github.com/caddyserver/caddy/issues/3958

[1] https://caddyserver.com/docs/caddyfile/directives/log

caddyconfig/httpcaddyfile/options_test.go

@@ -0,0 +1,64 @@
+package httpcaddyfile
+
+import (
+	"testing"
+
+	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
+	_ "github.com/caddyserver/caddy/v2/modules/logging"
+)
+
+func TestGlobalLogOptionSyntax(t *testing.T) {
+	for i, tc := range []struct {
+		input       string
+		output      string
+		expectError bool
+	}{
+		// NOTE: Additional test cases of successful Caddyfile parsing
+		// are present in: caddytest/integration/caddyfile_adapt/
+		{
+			input: `{
+				log default
+			}
+			`,
+			output:      `{}`,
+			expectError: false,
+		},
+		{
+			input: `{
+				log example {
+					output file foo.log
+				}
+				log example {
+					format json
+				}
+			}
+			`,
+			expectError: true,
+		},
+		{
+			input: `{
+				log example /foo {
+					output file foo.log
+				}
+			}
+			`,
+			expectError: true,
+		},
+	} {
+
+		adapter := caddyfile.Adapter{
+			ServerType: ServerType{},
+		}
+
+		out, _, err := adapter.Adapt([]byte(tc.input), nil)
+
+		if err != nil != tc.expectError {
+			t.Errorf("Test %d error expectation failed Expected: %v, got %v", i, tc.expectError, err)
+			continue
+		}
+
+		if string(out) != tc.output {
+			t.Errorf("Test %d error output mismatch Expected: %s, got %s", i, tc.output, out)
+		}
+	}
+}