Made a few available_options optional (will squash later)

I read the code from https://github.com/fastlane/fastlane/blob/master/fastlane_core/lib/fastlane_core/configuration/config_item.rb and tried to modernize the available_options.

Author: MarcPerezPro

lib/fastlane/plugin/aws_sns/actions/aws_sns_action.rb

@@ -151,22 +151,38 @@ def self.available_options
           FastlaneCore::ConfigItem.new(key: :access_key,
                                       env_name: "AWS_SNS_ACCESS_KEY",
                                       description: "AWS Access Key ID",
-                                      optional: false,
-                                      default_value: ENV['AWS_ACCESS_KEY_ID']),
+                                      optional: true,
+                                      sensitive: true,
+                                      conflicting_options: [:aws_sns_client],
+                                      conflict_block: proc do |value|
+                                        UI.user_error!("You can't use option '#{value.key}' along with 'access_key'")
+                                      end),
           FastlaneCore::ConfigItem.new(key: :secret_access_key,
                                       env_name: "AWS_SNS_SECRET_ACCESS_KEY",
                                       description: "AWS Secret Access Key",
-                                      optional: false,
-                                      default_value: ENV['AWS_SECRET_ACCESS_KEY']),
+                                      optional: true,
+                                      sensitive: true,
+                                      conflicting_options: [:aws_sns_client],
+                                      conflict_block: proc do |value|
+                                        UI.user_error!("You can't use option '#{value.key}' along with 'secret_access_key'")
+                                      end),
           FastlaneCore::ConfigItem.new(key: :region,
                                       env_name: "AWS_SNS_REGION",
                                       description: "AWS Region",
-                                      optional: false,
-                                      default_value: ENV['AWS_REGION']),
+                                      optional: true,
+                                      sensitive: true,
+                                      conflicting_options: [:aws_sns_client],
+                                      conflict_block: proc do |value|
+                                        UI.user_error!("You can't use option '#{value.key}' along with 'region'")
+                                      end),
           FastlaneCore::ConfigItem.new(key: :aws_sns_client,
                                       description: "AWS SNS Client, useful in case of special credentials or custom logging",
-                                      is_string: false,
-                                      optional: true),
+                                      type: Aws::SNS::Client,
+                                      optional: true,
+                                      conflicting_options: [:access_key, :secret_access_key, :region],
+                                      conflict_block: proc do |value|
+                                        UI.user_error!("You can't use option '#{value.key}' along with 'aws_sns_client'")
+                                      end),
           FastlaneCore::ConfigItem.new(key: :platform,
                                       env_name: "AWS_SNS_PLATFORM",
                                       description: "AWS Platform",
@@ -186,16 +202,19 @@ def self.available_options
                                       env_name: "AWS_SNS_PLATFORM_APNS_PRIVATE_KEY_PASSWORD",
                                       description: "AWS Platform APNS Private Key Password",
                                       optional: true,
+                                      sensitive: true,
                                       default_value: ""),
           FastlaneCore::ConfigItem.new(key: :platform_fcm_server_key,
                                       env_name: "AWS_SNS_PLATFORM_FCM_SERVER_KEY",
                                       description: "AWS Platform FCM SERVER KEY",
-                                      optional: true),
+                                      optional: true,
+                                      sensitive: true),
           FastlaneCore::ConfigItem.new(key: :platform_gcm_api_key,
                                       env_name: "AWS_SNS_PLATFORM_GCM_API_KEY",
                                       description: "AWS Platform GCM API KEY",
                                       deprecated: "Use :platform_fcm_server_key instead",
-                                      optional: true),
+                                      optional: true,
+                                      sensitive: true),
           FastlaneCore::ConfigItem.new(key: :update_if_exists,
                                       env_name: "AWS_SNS_UDPATE_IF_EXISTS",
                                       description: "updating certificate/key if platform_name already exists",