Target Domain as enviroment variable

[fititnt]

Tsuru best practices would recommend follow The twelve-factor app is a methodology, see https://12factor.net/. In this case ideally we should have one option to set the target domain only with environment variables and try to minimize need to the final user to change it's contents.

For now, since I'm configuring the https://www.etica.dev and not using CloudFlare free HTTPS, we have this issue compared with the https://aguia-pescadora.etica.ai:

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So, let's do this.