logging: Implement `log_append` handler (#6066)

* logging: Implement `extra_log` handler

* Rename to `log_append`

* Rename `skip_log` to `log_skip`

---------

Co-authored-by: Matt Holt <[email protected]>

2 files changed, 75 insertions, 4 deletions

diff --git a/caddytest/integration/caddyfile_adapt/log_add.caddyfiletest b/caddytest/integration/caddyfile_adapt/log_add.caddyfiletest
new file mode 100644
index 000000000..4f91e4644
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/log_add.caddyfiletest
@@ -0,0 +1,71 @@
+:80 {
+	log
+
+	vars foo foo
+
+	log_append const bar
+	log_append vars foo
+	log_append placeholder {path}
+
+	log_append /only-for-this-path secret value
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":80"
+					],
+					"routes": [
+						{
+							"handle": [
+								{
+									"foo": "foo",
+									"handler": "vars"
+								}
+							]
+						},
+						{
+							"match": [
+								{
+									"path": [
+										"/only-for-this-path"
+									]
+								}
+							],
+							"handle": [
+								{
+									"handler": "log_append",
+									"key": "secret",
+									"value": "value"
+								}
+							]
+						},
+						{
+							"handle": [
+								{
+									"handler": "log_append",
+									"key": "const",
+									"value": "bar"
+								},
+								{
+									"handler": "log_append",
+									"key": "vars",
+									"value": "foo"
+								},
+								{
+									"handler": "log_append",
+									"key": "placeholder",
+									"value": "{http.request.uri.path}"
+								}
+							]
+						}
+					],
+					"logs": {}
+				}
+			}
+		}
+	}
+}
diff --git a/caddytest/integration/caddyfile_adapt/log_except_catchall_blocks.caddyfiletest b/caddytest/integration/caddyfile_adapt/log_except_catchall_blocks.caddyfiletest
index 6fbc6c7c8..e1362f8fb 100644
--- a/caddytest/integration/caddyfile_adapt/log_except_catchall_blocks.caddyfiletest
+++ b/caddytest/integration/caddyfile_adapt/log_except_catchall_blocks.caddyfiletest
@@ -1,7 +1,7 @@
 http://localhost:2020 {
 	log
-	skip_log /first-hidden*
-	skip_log /second-hidden*
+	log_skip /first-hidden*
+	log_skip /second-hidden*
 	respond 200
 }
 
@@ -34,7 +34,7 @@ http://localhost:2020 {
 											"handle": [
 												{
 													"handler": "vars",
-													"skip_log": true
+													"log_skip": true
 												}
 											],
 											"match": [
@@ -49,7 +49,7 @@ http://localhost:2020 {
 											"handle": [
 												{
 													"handler": "vars",
-													"skip_log": true
+													"log_skip": true
 												}
 											],
 											"match": [