fix: restore context value class method

api/lib/opentelemetry/context.rb

@@ -12,6 +12,7 @@ module OpenTelemetry
   class Context
     KEY = :__opentelemetry_context__
     EMPTY_ENTRIES = {}.freeze
+    private_constant :KEY, :EMPTY_ENTRIES
 
     class << self
       # Returns a key used to index a value in a Context
@@ -102,6 +103,13 @@ def with_values(values)
         detach(prev)
       end
 
+      # Returns the value associated with key in the current context
+      #
+      # @param [String] key The lookup key
+      def value(key)
+        current.value(key)
+      end
+
       def clear
         self.current = ROOT
       end

api/test/opentelemetry/context_test.rb

@@ -213,6 +213,17 @@
     end
   end
 
+  describe '.value' do
+    it 'returns the value from the current context' do
+      Context.attach(new_context)
+      _(Context.value(foo_key)).must_equal('bar')
+
+      c2 = Context.current.set_value(bar_key, 'baz')
+      Context.attach(c2)
+      _(Context.value(bar_key)).must_equal('baz')
+    end
+  end
+
   describe '.clear' do
     it 'clears the context' do
       Context.attach(new_context)