[I18n] Update locale objects format (#23917) (#24639)

* Update output file format for i18n_check tool

* Update i18n engine to work with new format

* Update tests

* Fix UI bootstrap test

* Update loader tests and fix getTranslationsByLocale function

* Fix messages passing to IntlProvider

* Update messages interface

* Resolve comments

* Resolve comment

packages/kbn-i18n/src/__fixtures__/test_plugin_1/translations/en-US.json

@@ -1,4 +1,6 @@
 {
-  "a.b.c": "bar",
-  "d.e.f": "foo"
+  "messages": {
+    "a.b.c": "bar",
+    "d.e.f": "foo"
+  }
 }

packages/kbn-i18n/src/__fixtures__/test_plugin_1/translations/en.json

@@ -1,4 +1,6 @@
 {
-  "a.b.c": "foo",
-  "d.e.f": "bar"
+  "messages": {
+    "a.b.c": "foo",
+    "d.e.f": "bar"
+  }
 }

packages/kbn-i18n/src/__fixtures__/test_plugin_2/translations/en.json

@@ -1,4 +1,6 @@
 {
-  "a.b.c.custom": "foo.custom",
-  "d.e.f.custom": "bar.custom"
+  "messages": {
+    "a.b.c.custom": "foo.custom",
+    "d.e.f.custom": "bar.custom"
+  }
 }

packages/kbn-i18n/src/__fixtures__/test_plugin_2/translations/fr.json

@@ -1,3 +1,5 @@
 {
-  test: 'test' // JSON5 test
+  messages: {
+    test: 'test' // JSON5 test
+  }
 }

packages/kbn-i18n/src/__fixtures__/test_plugin_2/translations/ru.json

@@ -1,3 +1,5 @@
 {
-  "test": "test"
+  "messages": {
+    "test": "test"
+  }
 }

packages/kbn-i18n/src/angular/provider.ts

@@ -22,8 +22,8 @@ import * as i18n from '../core';
 export type I18nServiceType = ReturnType<I18nProvider['$get']>;
 
 export class I18nProvider implements angular.IServiceProvider {
-  public addMessages = i18n.addMessages;
-  public getMessages = i18n.getMessages;
+  public addTranslation = i18n.addTranslation;
+  public getTranslation = i18n.getTranslation;
   public setLocale = i18n.setLocale;
   public getLocale = i18n.getLocale;
   public setDefaultLocale = i18n.setDefaultLocale;

packages/kbn-i18n/src/core/__snapshots__/i18n.test.ts.snap

@@ -4,7 +4,7 @@ exports[`I18n engine addMessages should throw error if locale is not specified o
 
 exports[`I18n engine addMessages should throw error if locale is not specified or empty 2`] = `"[I18n] A \`locale\` must be a non-empty string to add messages."`;
 
-exports[`I18n engine addMessages should throw error if locale specified in messages is different from one provided as second argument 1`] = `"[I18n] A \`locale\` in the messages object is different from the one provided as a second argument."`;
+exports[`I18n engine addMessages should throw error if locale specified in messages is different from one provided as second argument 1`] = `"[I18n] A \`locale\` in the translation object is different from the one provided as a second argument."`;
 
 exports[`I18n engine translate should throw error if id is not a non-empty string 1`] = `"[I18n] An \`id\` must be a non-empty string to translate a message."`;