Improve logging

- Actually log useful information at their respective log level.
- Add logs in hot-paths to be able to deep-dive and debug specific
requests (see server/handler.go)
- Remove zerologger and instead use custom logger that doesn't log
JSON (directly inspired by https://codeberg.org/Codeberg/moderation/pulls/7).
- Add more information to existing fields(e.g. the host that the user is
visiting, this was noted by @fnetX).

cmd/flags.go

@@ -5,12 +5,6 @@ import (
 )
 
 var ServeFlags = []cli.Flag{
-	&cli.BoolFlag{
-		Name: "verbose",
-		// TODO: Usage
-		EnvVars: []string{"DEBUG"},
-	},
-
 	// MainDomainSuffix specifies the main domain (starting with a dot) for which subdomains shall be served as static
 	// pages, or used for comparison in CNAME lookups. Static pages can be accessed through
 	// https://{owner}.{MainDomain}[/{repo}], with repo defaulting to "pages".
@@ -69,6 +63,24 @@ var ServeFlags = []cli.Flag{
 		// TODO: desc
 		EnvVars: []string{"ENABLE_HTTP_SERVER"},
 	},
+	&cli.StringSliceFlag{
+		Name:    "log-output",
+		Value:   cli.NewStringSlice("console"),
+		Usage:   "specify where the log will be outputed. Multiple options can be chosen, possible options: console, file",
+		EnvVars: []string{"LOG_OUTPUT"},
+	},
+	&cli.StringFlag{
+		Name:    "log-level",
+		Value:   "warn",
+		Usage:   "specify at which log level should be logged. Possible options: info, warn, error, fatal",
+		EnvVars: []string{"LOG_LEVEL"},
+	},
+	&cli.StringFlag{
+		Name:    "log-file",
+		Value:   "pages-server.log",
+		Usage:   "specify the log file. Only applies when file logging is enabled",
+		EnvVars: []string{"LOG_FILE"},
+	},
 
 	// ACME
 	&cli.StringFlag{