Added elastic-apm gem and its config file

• Added:
- elastic-apm gem and its config file elastic_apm.yml

Gemfile

@@ -150,3 +150,5 @@ group :production do
 end
 
 gem 'concurrent-ruby', require: false
+
+gem "elastic-apm", "~> 3.10"

Gemfile.lock

@@ -192,6 +192,9 @@ GEM
     dotenv-rails (2.7.2)
       dotenv (= 2.7.2)
       railties (>= 3.2, < 6.1)
+    elastic-apm (3.10.1)
+      concurrent-ruby (~> 1.0)
+      http (>= 3.0)
     elasticsearch (6.0.2)
       elasticsearch-api (= 6.0.2)
       elasticsearch-transport (= 6.0.2)
@@ -682,6 +685,7 @@ DEPENDENCIES
   devise_pam_authenticatable2 (~> 9.2)
   doorkeeper (~> 5.1)
   dotenv-rails (~> 2.7)
+  elastic-apm (~> 3.10)
   fabrication (~> 2.20)
   faker (~> 1.9)
   fast_blank (~> 1.0)

config/elastic_apm.yml

@@ -0,0 +1,11 @@
+# config/elastic_apm.yml:
+
+# Set service name - allowed characters: a-z, A-Z, 0-9, -, _ and space
+# Defaults to the name of your Rails app
+service_name: <%= ENV['ES_APM_SERVICE_NAME'] %>
+
+# Use if APM Server requires a token
+secret_token: <%= ENV['ES_APM_SECRET_TOKEN'] %>
+
+# Set custom APM Server URL (default: http://localhost:8200)
+server_url: <%= ENV['ES_APM_URL'] %>