refactor: implement surname_initials method and update references for consistency

lab2/README.md

@@ -30,6 +30,7 @@ classDiagram
         + phone=(String) : Boolean
         + telegram=(String) : Boolean
         + email=(String) : Boolean
+        + surname_initials() : NotImplementedError
         + valid_phone_number() : Boolean <<class>>
         + valid_telegram() : Boolean <<class>>
         + valid_email() : Boolean <<class>>

lab2/main.rb

@@ -21,7 +21,7 @@ def test_classes
     email: 'ivanov@example.com'
   )
   puts "Student Full Info: #{student.to_s}"
-  puts "Student Initials: #{student.surname_and_initials}"
+  puts "Student Initials: #{student.surname_initials}"
   puts "Student Contact Info: #{student.get_first_contact}"
 
   student_short = StudentShort.from_student(student)

lab2/person.rb

@@ -12,6 +12,10 @@ class Person
     @git = git
   end
 
+  def surname_initials
+    raise NotImplementedError, "#{self.class} must implement the 'surname_initials' method"
+  end
+
   def git_present?
     !@git.nil? && !@git.empty?
   end

lab2/student_short.rb

@@ -12,7 +12,7 @@ class StudentShort < Person
   def self.from_student(student)
     new(
       id: student.id,
-      surname_initials: student.surname_and_initials,
+      surname_initials: student.surname_initials,
       phone: student.phone,
       telegram: student.telegram,
       email: student.email