Use Staging Price API Endpoint for development and PR branches

[Velenir]

Link to a different price estimation service based on deployment

• By default: Use the production ones
• PR + Develop: Use their staging

For example. It could be implemented in travis by having a logic depending on the branch:

if (
   branch <> master OR
   is not a tag
) {
   BACEND_URL = 1234
}

Not sure what is the cleanest way to do it, but travis allows to set rules by branch. Also that the in the shell script, it exposes information as environemt variable to build this conditional behaviour.