refactor: use associative array for existing options

Use Bash's associative array for the existing configuration options and
for the translation of something like "DBUSER" to "dbUser", replacing
the for loop that existed before.

entrypoint.sh

@@ -9,6 +9,13 @@ readonly CONFIG_REGEX="^(\;|\#)?\ *([a-zA-Z_0-9]+)=.*"
 # Compile list of configuration options from the bare-bones config
 readarray -t existing_config_options < <(sed -En "s/$CONFIG_REGEX/\2/p" "$BARE_BONES_CONFIG_FILE")
 
+# Create an associative array for faster config option lookup
+declare -A config_from_uppercase
+
+for config in "${existing_config_options[@]}"; do
+	config_from_uppercase["${config^^}"]="$config"
+done
+
 # Grab the original command line that is supposed to start the Mumble server
 declare -a server_invocation=("${@}")
 declare -a used_configs
@@ -54,25 +61,16 @@ else
 	# Process settings through variables of format MUMBLE_CONFIG_*
 
 	while IFS='=' read -d '' -r var value; do
-		# MUMBLE_CONFIG_DB_BLA and MUMBLE_CONFIG_DBBLA mean the same
-		uppercase_variable=${var/MUMBLE_CONFIG_/}
-		uppercase_variable_no_underscores="${uppercase_variable//_/}"
-		found=false
+		# Uppercase and remove underscores so MUMBLE_CONFIG_A_B == MUMBLE_CONFIG_AB
+		uppercase_variable="${var/MUMBLE_CONFIG_/}"
+		config_option="${config_from_uppercase[${uppercase_variable//_/}]}"
 
-		for current_config in "${existing_config_options[@]}"; do
-			uppercase_current_config=${current_config^^}
-
-			if [[ "$uppercase_current_config" = "$uppercase_variable" || "$uppercase_current_config" = "$uppercase_variable_no_underscores" ]]; then
-				set_config "$current_config" "$value"
-				found=true
-				break
-			fi
-		done
-
-		if [[ "$found" = "false" ]]; then
+		if [[ -z "$config_option" ]]; then
 			>&2 echo "[ERROR]: Unable to find config corresponding to variable \"$var\""
 			exit 1
 		fi
+
+		set_config "$config_option" "$value"
 	done < <( printenv --null | grep -az MUMBLE_CONFIG_ ) # Feeding it in like this, prevents the creation of a subshell for the while-loop
 
 	# Apply default settings if they're missing