refactor: improve type signatures

- Add typed: strict sigil and signatures to Utils
- Use T::Hash[Symbol, T.untyped] for create_code_team attributes
- Fix nilable string handling in Plugin.default_data_accessor_name

Author: joemsak

lib/code_teams/plugin.rb

@@ -25,7 +25,7 @@ def self.data_accessor_name(key = default_data_accessor_name)
     sig { returns(String) }
     def self.default_data_accessor_name
       # e.g., MyNamespace::MyPlugin -> my_plugin
-      Utils.underscore(Utils.demodulize(name))
+      Utils.underscore(Utils.demodulize(T.must(name)))
     end
 
     sig { params(base: T.untyped).void }

lib/code_teams/testing.rb

@@ -40,14 +40,14 @@ def self.enable!
       end
     end
 
-    sig { params(attributes: T::Hash[T.untyped, T.untyped]).returns(CodeTeams::Team) }
+    sig { params(attributes: T::Hash[Symbol, T.untyped]).returns(CodeTeams::Team) }
     def self.create_code_team(attributes)
       attributes = attributes.dup
       attributes[:name] ||= "Fake Team #{SecureRandom.hex(4)}"
 
       code_team = CodeTeams::Team.new(
         config_yml: 'tmp/fake_config.yml',
-        raw_hash: T.cast(Utils.deep_stringify_keys(attributes), T::Hash[T.untyped, T.untyped])
+        raw_hash: Utils.deep_stringify_keys(attributes)
       )
 
       code_teams << code_team

lib/code_teams/utils.rb

@@ -1,7 +1,14 @@
+# frozen_string_literal: true
+#
+# typed: strict
+
 module CodeTeams
   module Utils
+    extend T::Sig
+
     module_function
 
+    sig { params(string: String).returns(String) }
     def underscore(string)
       string.gsub('::', '/')
         .gsub(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
@@ -10,10 +17,13 @@ def underscore(string)
         .downcase
     end
 
+    sig { params(string: String).returns(String) }
     def demodulize(string)
-      string.split('::').last
+      T.must(string.split('::').last)
     end
 
+    # Recursively converts symbol keys to strings. Top-level input should be a Hash.
+    sig { params(value: T.untyped).returns(T.untyped) }
     def deep_stringify_keys(value)
       case value
       when Hash