[feature] Make log format configurable (#2130)

* [feature] Don't emit timestamp in log lines

When running gotosocial with a service manager like systemd, or a
container runtime, the associated log driver usually emits timestamps
itself. In those cases, having the extra timestamp from our own log
lines ends up being a bit noisy and when centrally ingesting logs is
duplicate information.

This introduces a configuration flag that allows disabling emitting the
timestamp. It's only wired up for "daemonised" processes, meaning server
and testrig.

* [chore] Add docs for log-timestamp

* [feature] Simplify timestamp handling

Co-Authored-By: kim <89579420+NyaaaWhatsUpDoc@users.noreply.github.com>

* [chore] Less escaped double-quotes

* [chore] Fix help string

---------

Co-authored-by: kim <89579420+NyaaaWhatsUpDoc@users.noreply.github.com>

testrig/config.go

@@ -33,17 +33,18 @@ func InitTestConfig() {
 }
 
 var testDefaults = config.Configuration{
-	LogLevel:        "info",
-	LogDbQueries:    true,
-	ApplicationName: "gotosocial",
-	LandingPageUser: "",
-	ConfigPath:      "",
-	Host:            "localhost:8080",
-	AccountDomain:   "localhost:8080",
-	Protocol:        "http",
-	BindAddress:     "127.0.0.1",
-	Port:            8080,
-	TrustedProxies:  []string{"127.0.0.1/32", "::1"},
+	LogLevel:           "info",
+	LogTimestampFormat: "02/01/2006 15:04:05.000",
+	LogDbQueries:       true,
+	ApplicationName:    "gotosocial",
+	LandingPageUser:    "",
+	ConfigPath:         "",
+	Host:               "localhost:8080",
+	AccountDomain:      "localhost:8080",
+	Protocol:           "http",
+	BindAddress:        "127.0.0.1",
+	Port:               8080,
+	TrustedProxies:     []string{"127.0.0.1/32", "::1"},
 
 	DbType:                   "sqlite",
 	DbAddress:                ":memory:",