Allow log level to be set at runtime (#267)

I noticed we never allow overriding of the log level from Info, even
though we do log at lower levels. This provides a mechanism to fix this
- I thought it might be potentially helpful in debugging population
errors (as #264 might be).

This partially depends on, and therefore has some similar diffs to,
#266.

Default output:

![image](https://github.com/user-attachments/assets/289cbb49-fe0d-42aa-badf-534f4f0f50f4)

With level=Debug (and the ideal Cadence dev music folder):

![image](https://github.com/user-attachments/assets/04e7d23f-6960-4efc-afef-94e4edf29bfe)

Commandline that sets Debug:

![image](https://github.com/user-attachments/assets/1961cb28-d4a1-4cca-8b53-498e8aba6955)

config/cadence.env.example

@@ -3,13 +3,14 @@ CSERVER_REQRATELIMIT=CADENCE_RATE_EXAMPLE
 POSTGRES_PASSWORD=CADENCE_PASS_EXAMPLE
 
 # ####################################################
-# If you are running Cadence through Docker simply as a user, 
+# If you are running Cadence through Docker simply as a user,
 # you are unlikely to ever need to change anything below.
 
 # Development
 CSERVER_DEVMODE=0
 CSERVER_VERSION=5.4.4
 CSERVER_ROOTPATH=/cadence/server/
+CSERVER_LOGLEVEL=info
 
 # Service Addresses
 CSERVER_PORT=:8080

src/server/main.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"os"
 	"strconv"
+	"strings"
 )
 
 var c = ServerConfig{}
@@ -31,6 +32,27 @@ type ServerConfig struct {
 	RedisPort         string
 	WhitelistPath     string
 	DevMode           bool
+	LogLevel          string
+}
+
+func parseLogLevel(level string) slog.Level {
+	if level == "" {
+		return slog.LevelInfo
+	}
+
+	switch strings.ToLower(level) {
+	case "debug":
+		return slog.LevelDebug
+	case "info":
+		return slog.LevelInfo
+	case "warn":
+		return slog.LevelWarn
+	case "error":
+		return slog.LevelError
+	default:
+		slog.Warn(fmt.Sprintf("Unrecognized log level %s!", level), "func", "parseLogLevel")
+		return slog.LevelInfo
+	}
 }
 
 func main() {
@@ -54,6 +76,9 @@ func main() {
 	c.RedisPort = os.Getenv("CSERVER_REDISPORT")
 	c.WhitelistPath = os.Getenv("CSERVER_WHITELIST_PATH")
 	c.DevMode, _ = strconv.ParseBool(os.Getenv("CSERVER_DEVMODE"))
+	c.LogLevel = os.Getenv("CSERVER_LOGLEVEL")
+
+	slog.SetLogLoggerLevel(parseLogLevel(c.LogLevel))
 
 	if postgresInit() == nil {
 		if postgresPopulate() != nil {