Add test about base_url provided in client (#456)

`base_url` option provided by all client is useful for using a mock
server, changing base url due to some reasons, or testing locally(though
we have webmock... in this project).
This change adds tests for it.

Author: Yang-33

spec/line/bot/v2/misc_spec.rb

@@ -1,4 +1,5 @@
 require 'spec_helper'
+require 'base64'
 
 describe 'misc' do
   let(:channel_access_token) { 'YOUR_CHANNEL_ACCESS_TOKEN' }
@@ -672,6 +673,88 @@
     end
   end
 
+  describe 'Client.new - base_url' do
+    describe 'normal client' do
+      let(:client) { Line::Bot::V2::MessagingApi::ApiClient.new(channel_access_token: 'test-channel-access-token', base_url: 'https://example.com') }
+      let(:user_id) { 'u1234567890' }
+      let(:response_body) { { displayName: "LINE taro", userId: user_id, language: "en", pictureUrl: "https://profile.line-scdn.net/ch/v2/p/uf9da5ee2b...", statusMessage: "Hello, LINE!" }.to_json }
+      let(:response_code) { 200 }
+
+      it 'allow to change base_url in normal client' do
+        path = "https://example.com/v2/bot/profile/#{user_id}"
+        stub_request(:get, path)
+          .with(
+            headers: {
+              'Authorization' => "Bearer test-channel-access-token"
+            }
+          )
+          .to_return(status: response_code, body: response_body, headers: { 'Content-Type' => 'application/json' })
+
+        body, status_code, headers = client.get_profile_with_http_info(user_id: user_id)
+
+        expect(status_code).to eq(response_code)
+        expect(body.user_id).to eq(user_id)
+      end
+    end
+
+    describe 'blob client' do
+      let(:client) { Line::Bot::V2::MessagingApi::ApiBlobClient.new(channel_access_token: 'test-channel-access-token', base_url: 'https://example.com') }
+      let(:response_body) { { status: "succeeded" }.to_json }
+      let(:response_code) { 200 }
+
+      it 'allow to change base_url in blob client' do
+        path = "https://example.com/v2/bot/message/test-message-id/content/transcoding"
+        stub_request(:get, path)
+          .with(
+            headers: {
+              'Authorization' => "Bearer test-channel-access-token"
+            }
+          )
+          .to_return(status: response_code, body: response_body, headers: { 'Content-Type' => 'application/json' })
+
+        body, status_code, headers = client.get_message_content_transcoding_by_message_id_with_http_info(message_id: 'test-message-id')
+        expect(status_code).to eq(200)
+        expect(body.status).to eq('succeeded')
+      end
+    end
+
+    describe 'module attach client' do
+      let(:client) { Line::Bot::V2::ModuleAttach::ApiClient.new(base_url: 'https://example.com', channel_id: '100000', channel_secret: 'test-channel-secret') }
+      let(:response_body) { { bot_id: "U111...", scopes: ["message:send", "message:receive"] }.to_json }
+      let(:response_code) { 200 }
+
+      it 'allow to change base_url in module attach client' do
+        path = "https://example.com/module/auth/v1/token"
+        expected_authorization_header_value = Base64.strict_encode64("100000:test-channel-secret")
+
+        stub_request(:post, path)
+          .with(
+            headers: {
+              'Authorization' => "Basic #{expected_authorization_header_value}",
+              'Content-Type' => 'application/x-www-form-urlencoded'
+            },
+            body: {
+              'grant_type' => 'authorization_code',
+              'code' => 'test-code',
+              'redirect_uri' => 'https://example2.com/callback?key=value',
+              'scope' => 'message:send message:receive'
+            }
+          )
+          .to_return(status: response_code, body: response_body, headers: { 'Content-Type' => 'application/json' })
+
+        body, status_code, headers = client.attach_module_with_http_info(
+          grant_type: 'authorization_code',
+          code: 'test-code',
+          redirect_uri: 'https://example2.com/callback?key=value',
+          scope: 'message:send message:receive'
+        )
+        expect(status_code).to eq(200)
+        expect(body.bot_id).to eq('U111...')
+        expect(body.scopes).to eq(["message:send", "message:receive"])
+      end
+    end
+  end
+
   describe 'Line::Bot::V2::MessagingApi::TemplateMessage#initialize' do
     it "contains fixed type attribute" do
       template_message = Line::Bot::V2::MessagingApi::TemplateMessage.new(