Resolve "Refactor how PNDs are implemented in the code"

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Closes #243

controller/controller.go

@@ -291,13 +291,22 @@ func ensureDefaultUserExists() error {
 	if err != nil {
 		log.Info(err)
 	}
-
 	if adminUser == nil {
-		// Generate a password that is 16 characters long with 3 digits, 0 symbols,
-		// allowing upper and lower case letters, disallowing repeat characters.
-		generatedPassword, err := password.Generate(16, 3, 0, true, false)
-		if err != nil {
-			log.Fatal(err)
+		// Getting the password from the environment variable which is set in gosdn.clab.yaml.
+		var preDefinedPassword = os.Getenv("GOSDN_ADMIN_PASSWORD")
+		var usedPassword string
+
+		// If environment variable is set and password is not 0, the password from the environment variable will be used.
+		if len(preDefinedPassword) == 0 {
+			// Generate a password that is 16 characters long with 3 digits, 0 symbols,
+			// allowing upper and lower case letters, disallowing repeat characters.
+			generatedPassword, err := password.Generate(16, 3, 0, true, false)
+			if err != nil {
+				log.Fatal(err)
+			}
+			usedPassword = generatedPassword
+		} else {
+			usedPassword = preDefinedPassword
 		}
 
 		salt, err := password.Generate(16, 3, 0, true, false)
@@ -305,14 +314,14 @@ func ensureDefaultUserExists() error {
 			log.Fatal(err)
 		}
 
-		hashedPassword := base64.RawStdEncoding.EncodeToString(argon2.IDKey([]byte(generatedPassword), []byte(salt), 1, 64*1024, 4, 32))
+		hashedPassword := base64.RawStdEncoding.EncodeToString(argon2.IDKey([]byte(usedPassword), []byte(salt), 1, 64*1024, 4, 32))
 
 		err = c.userService.Add(rbacImpl.NewUser(uuid.New(), defaultUserName, map[string]string{config.BasePndUUID.String(): "admin"}, string(hashedPassword), "", salt, conflict.Metadata{}))
 		if err != nil {
 			return err
 		}
 
-		fmt.Printf("########\n Generated admin password: %s\n########\n", generatedPassword)
+		fmt.Printf("########\n Generated admin password: %s\n########\n", usedPassword)
 	}
 
 	return nil