docs: enhance assert_changes and assert_no_changes documentation

Added comprehensive examples demonstrating case equality and type checking
capabilities of the assert_changes and assert_no_changes methods.
The examples show how these methods can be used with exact value matches,
regular expressions, and class type checks using the case equality (===) operator.

Author: saiqulhaq

activesupport/lib/active_support/testing/assertions.rb

@@ -181,12 +181,24 @@ def assert_no_difference(expression, message = nil, &block)
       #
       # The keyword arguments +:from+ and +:to+ can be given to specify the
       # expected initial value and the expected value after the block was
-      # executed.
+      # executed. The comparison is done using case equality (===), which means
+      # you can specify patterns or classes:
       #
+      #   # Exact value match
       #   assert_changes :@object, from: nil, to: :foo do
       #     @object = :foo
       #   end
       #
+      #   # Case equality
+      #   assert_changes -> { user.token }, to: /\w{32}/ do
+      #     user.generate_token
+      #   end
+      #
+      #   # Type check
+      #   assert_changes -> { current_error }, from: nil, to: RuntimeError do
+      #     raise "Oops"
+      #   end
+      #
       # An error message can be specified.
       #
       #   assert_changes -> { Status.all_good? }, 'Expected the status to be bad' do
@@ -238,12 +250,24 @@ def assert_changes(expression, message = nil, from: UNTRACKED, to: UNTRACKED, &b
       #   end
       #
       # Provide the optional keyword argument +:from+ to specify the expected
-      # initial value.
+      # initial value. The comparison is done using case equality (===), which means
+      # you can specify patterns or classes:
       #
+      #   # Exact value match
       #   assert_no_changes -> { Status.all_good? }, from: true do
       #     post :create, params: { status: { ok: true } }
       #   end
       #
+      #   # Case equality
+      #   assert_no_changes -> { user.token }, from: /\w{32}/ do
+      #     user.touch
+      #   end
+      #
+      #   # Type check
+      #   assert_no_changes -> { current_error }, from: RuntimeError do
+      #     retry_operation
+      #   end
+      #
       # An error message can be specified.
       #
       #   assert_no_changes -> { Status.all_good? }, 'Expected the status to be good' do