[swift5] Define models and Configuration classes under namespace

When swiftUseApiNamespace is set, API classes get defined under the
projectName namespace. This does the same for models and the
Configuration class. Plus adding a deprecation warning when using the
un-namespaced variants.

modules/openapi-generator/src/main/resources/swift5/Configuration.mustache

@@ -6,9 +6,18 @@
 
 import Foundation
 
+{{#swiftUseApiNamespace}}
+@available(*, deprecated, renamed: "{{projectName}}.Configuration")
+{{#nonPublicApi}}internal{{/nonPublicApi}}{{^nonPublicApi}}public{{/nonPublicApi}} typealias Configuration = {{projectName}}.Configuration
+
+extension {{projectName}} {
+{{/swiftUseApiNamespace}}
 {{#nonPublicApi}}internal{{/nonPublicApi}}{{^nonPublicApi}}open{{/nonPublicApi}} class Configuration {
     // This value is used to configure the date formatter that is used to serialize dates into JSON format.
     // You must set it prior to encoding any dates, and it will only be read once.
     @available(*, unavailable, message: "To set a different date format, use CodableHelper.dateFormatter instead.")
     {{#nonPublicApi}}internal{{/nonPublicApi}}{{^nonPublicApi}}public{{/nonPublicApi}} static var dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ"
 }
+{{#swiftUseApiNamespace}}
+}
+{{/swiftUseApiNamespace}}

modules/openapi-generator/src/main/resources/swift5/model.mustache

@@ -9,11 +9,21 @@ import Foundation
 #if canImport(AnyCodable)
 import AnyCodable
 #endif
-{{#description}}
 
+{{#swiftUseApiNamespace}}
+@available(*, deprecated, renamed: "{{projectName}}.{{classname}}")
+{{#nonPublicApi}}internal{{/nonPublicApi}}{{^nonPublicApi}}public{{/nonPublicApi}} typealias {{classname}} = {{projectName}}.{{classname}}
+
+extension {{projectName}} {
+{{/swiftUseApiNamespace}}
+
+{{#description}}
 /** {{description}} */{{/description}}{{#isDeprecated}}
 @available(*, deprecated, message: "This schema is deprecated."){{/isDeprecated}}{{#vendorExtensions.x-is-one-of-interface}}
 {{> modelOneOf}}{{/vendorExtensions.x-is-one-of-interface}}{{^vendorExtensions.x-is-one-of-interface}}{{#isArray}}
 {{> modelArray}}{{/isArray}}{{^isArray}}{{#isEnum}}
 {{> modelEnum}}{{/isEnum}}{{^isEnum}}
 {{> modelObject}}{{/isEnum}}{{/isArray}}{{/vendorExtensions.x-is-one-of-interface}}{{/model}}{{/models}}
+{{#swiftUseApiNamespace}}
+}
+{{/swiftUseApiNamespace}}