Rename handler_dir to handler_plugin_dir in configuration and update related tests. All refs to the handler dir must be made through handler_plugin_dir going forward to be consistent

Author: GrantBirki

docs/design.md

@@ -109,7 +109,7 @@ export HOOKS_ROOT_PATH="/webhooks"
 export HOOKS_LOG_LEVEL=info
 
 # Paths
-export HOOKS_HANDLER_DIR=./handlers
+export HOOKS_HANDLER_PLUGIN_DIR=./handlers
 export HOOKS_HEALTH_PATH=/health
 export HOOKS_VERSION_PATH=/version
 
@@ -163,7 +163,7 @@ lib/hooks/
 ```yaml
 # config/endpoints/team1.yaml
 path: /team1                  # Mounted at <root_path>/team1
-handler: Team1Handler         # Class in handler_dir
+handler: Team1Handler         # Class in handler_plugin_dir
 
 # Signature validation
 auth:
@@ -181,7 +181,7 @@ opts:                         # Freeform user-defined options
 
 ```yaml
 # config/config.yaml
-handler_dir:     ./handlers         # handler class directory
+handler_plugin_dir:     ./handlers         # handler class directory
 log_level:       info               # debug | info | warn | error
 
 # Request handling
@@ -345,7 +345,7 @@ app = Hooks.build(
 
 **Handler & Plugin Discovery:**
 
-* Handler classes are auto-discovered from `handler_dir` using file naming convention
+* Handler classes are auto-discovered from `handler_plugin_dir` using file naming convention
 * File `team1_handler.rb` → class `Team1Handler`
 * Plugin classes are loaded from `plugin_dir` and registered based on class inheritance
 * All classes must inherit from appropriate base classes to be recognized

lib/hooks/core/config_loader.rb

@@ -127,7 +127,6 @@ def self.load_env_config
         env_config = {}
 
         env_mappings = {
-          "HOOKS_HANDLER_DIR" => :handler_dir,
           "HOOKS_HANDLER_PLUGIN_DIR" => :handler_plugin_dir,
           "HOOKS_AUTH_PLUGIN_DIR" => :auth_plugin_dir,
           "HOOKS_LIFECYCLE_PLUGIN_DIR" => :lifecycle_plugin_dir,

lib/hooks/core/config_validator.rb

@@ -12,7 +12,6 @@ class ValidationError < StandardError; end
 
       # Global configuration schema
       GLOBAL_CONFIG_SCHEMA = Dry::Schema.Params do
-        optional(:handler_dir).filled(:string)  # For backward compatibility
         optional(:handler_plugin_dir).filled(:string)
         optional(:auth_plugin_dir).maybe(:string)
         optional(:lifecycle_plugin_dir).maybe(:string)

spec/unit/lib/hooks/core/config_validator_spec.rb

@@ -5,7 +5,7 @@
     context "with valid configuration" do
       it "returns validated configuration with all optional fields" do
         config = {
-          handler_dir: "./custom_handlers",
+          handler_plugin_dir: "./custom_handlers",
           log_level: "debug",
           request_limit: 2_048_000,
           request_timeout: 45,
@@ -101,7 +101,7 @@
 
       it "raises ValidationError for empty string values" do
         config = {
-          handler_dir: "",
+          handler_plugin_dir: "",
           root_path: "",
           health_path: ""
         }
@@ -125,7 +125,7 @@
 
       it "raises ValidationError for non-string paths" do
         config = {
-          handler_dir: 123,
+          handler_plugin_dir: 123,
           root_path: [],
           endpoints_dir: {}
         }