rails 5.2 credentials capistrano deploy 的各種坑

Deploy 一直遇到 Error:

```
ArgumentError: Missing `secret_key_base` for 'production' environment, set this string with `rails credentials:edit`
```

試了好多方式，理論上設個環境變數就行，但我一直失敗，中途還嘗試把credentials disable 也是沒用，後來是直接上傳 master.key 解決


用這行指令上傳
```
scp config/master.key apps@DOMAIN:PROJECT_NAME/shared/config
```

然後 capistrano link 過去
```
set :linked_files, fetch(:linked_files, []).push("config/database.yml", "config/master.key"
```


http://guides.rubyonrails.org/security.html#custom-credentials
https://keithpblog.org/post/encrypted-secrets/
https://github.com/rails/rails/issues/32413