Add design section.

metrics/cli/docs/04_managing_firestore_data.md

@@ -34,9 +34,17 @@ The `dartbase_admin` package requires the following parameters:
 
 2. The JSON of the service account's key, which can be downloaded using the following command:
 
-```bash
-gcloud iam service-accounts keys create key.json --iam-account [email protected]
-```
+    ```bash
+    gcloud iam service-accounts keys create key.json --iam-account [email protected]
+    ```
+
+    _**Note**: The above-described key is a `private key` for the chosen service account, which requires additional secure factors when working with it. 
+    Therefore, to make sure the user does not need to worry about managing created `private key`, the CLI tool should deactivate the `key` after finishing work with it using the following command:_
+
+    ```bash
+    gcloud iam service-accounts keys delete KEY-ID [email protected]
+    ```
+
 
 Example of creating document using dart package:
 
@@ -112,3 +120,34 @@ Cons:
 ### Decision
 
 As we've analyzed above, the [Cloud Functions](#using-cloud-functions-for-firebase) does not allow us to automate the Cloud Firestore data managing, so we should choose the [Dart Package](#using-dart-package) since it provides a more clean and fully automated way of managing Cloud Firestore data.
+
+## Design
+
+The following sections provide an implementation of managing Firestore data integration into the Metrics CLI tool. 
+
+Let's take a look on the main classes the managing firestore data integration requires.
+
+### FirestoreConfigRepository
+
+The `FirestoreConfigRepository` is a repository, which provides methods for managing the [feature config](https://github.com/platform-platform/monorepo/blob/master/docs/19_security_audit_document.md#the-feature_config-collection) 
+and [allowed domains](https://github.com/platform-platform/monorepo/blob/master/docs/19_security_audit_document.md#the-allowed_email_domains-collection) collections data. For this, purposes the repository using the [dartbase_admin package](https://pub.dev/packages/dartbase_admin) as described in the [decision](#decision).
+
+### FirebaseService
+
+The `FirebaseService` is an existing service interface, in which we should add the following methods required for this integration:
+- `seedFirestoreData` - seeds Firestore database with required data;
+- `initAdminFirestore` - initializes Firestore database with Admin privileges.
+
+### GcloudService
+
+The `GcloudService` is an existing service interface, in which we should add the following methods required for this integration:
+- `downloadServiceKey` - downloads a service account's key;
+- `deactivateServiceKey` - deactivates a service account's key.
+
+### FirebaseServiceAdapter
+
+The `FirebaseServiceAdapter` is an adapter for the [`FirebaseService`](#FirebaseService), which implements new added features using the [`FirestoreConfigRepository`](#FirestoreConfigRepository) and the [dartbase_admin package](https://pub.dev/packages/dartbase_admin).
+
+Here is a class diagram, which demonstrates the structure and relationships of classes the Managing Firestore data integration requires:
+
+![Managing Firestore Data class diagram](http://www.plantuml.com/plantuml/proxy?cache=no&fmt=svg&src=https://github.com/platform-platform/monorepo/raw/design_doc_firestore_data/metrics/cli/docs/diagrams/managing_firestore_data_class_diagram.puml)

metrics/cli/docs/diagrams/managing_firestore_data_class_diagram.puml

@@ -0,0 +1,74 @@
+@startuml firestore_managing_data_class_diagram
+
+package firebase {
+    package service as firebase.service {
+        interface FirebaseService {
+            + login(): Future<String>
+            + addProject(String gcloudProjectId): Future<void>
+            + initAdminFirestore(String projectId, String service) : Future<void>
+            + seedFirestoreData() : Future<void>
+            + deployHosting(String appPath): Future<void>
+            + deployFirestore(String firestorePath): Future<void>
+        }
+    }
+
+    package adapter as firebase.adapter {
+        class FirebaseServiceAdapter {
+            - _firebaseCli: FirebaseCli
+            - _firestoreConfigRepository: FirestoreConfigRepository
+        }
+    }
+
+    package cli as firebase.cli {
+        class FirebaseCli {
+        }
+    }
+
+    package repository as firebase.repository {
+        class FirestoreConfigRepository {
+            - _firestore : Firestore
+            + addAllowedDomain(String domain) : Future<void>
+            + setFeatureConfig(bool isPasswordSignInOptionEnabled, bool isDebugMenuEnabled): Future<void>
+        }
+    }
+}
+
+package interfaces {
+    package service {
+        interface InfoService {
+            + version() : Future<void>
+        }
+    }
+}
+
+package core {
+    package data.model {
+        class FeatureConfigData {
+            + Map<String, dynamic> toJson()
+            + factory fromJson(Map<String, dynamic> json)
+        }
+    }
+
+    package domain.entities {
+        class FeatureConfig {
+            + isPasswordSignInOptionEnabled : bool
+            + isDebugMenuEnabled : bool
+        }
+    }
+}
+
+package dartbase_admin {
+}
+
+FirebaseService --|> InfoService
+FeatureConfigData --|> FeatureConfig
+
+FirebaseServiceAdapter ..|> FirebaseService
+FirebaseServiceAdapter --> FirebaseCli : uses
+FirebaseServiceAdapter --> FirestoreConfigRepository : uses
+FirebaseServiceAdapter -up-> dartbase_admin : uses
+
+FirestoreConfigRepository -up-> dartbase_admin : uses
+FirestoreConfigRepository --> FeatureConfigData : uses
+
+@enduml