[Documentation] Add default values to environment variables

[T3rm1]

I wanted to create a minimal setup and was overwhelmed by the amount of configuration options in the .env file. Unfortunately neither the example file nor the documentation page states what the default value of each parameter is.

My goal was to start with an empty env file and only change what is necessary - to keep it simple. It's crucial to know what the default for various parameters is, e.g. MONGO_MAX_POOL_SIZE.

At first, I thought that the example might be also the default value but that is not the case. I tested it by removing PORT from the file and the application would no longer start.

[danny-avila]

Any issue using .env.example as a starting point? We can definitely add more documentation to it and improve it

[T3rm1]

It has too many actual entries. It's not clear why they are there. The only logical reason is that the default value differs. But this begs the question why.
In my opinion every single value in the example should be commented out. Set reasonable defaults so this is possible. Only if the user wants to configure something differently he should be required to change something.

Lets take MONGO_MAX_POOL_SIZE as an example. This is set to an empty string in the file. I assume this means unlimited. But I don't know what would happen if I comment it out. What is the default value?
If the default is also unlimited -> # MONGO_MAX_POOL_SIZE=
If the default is 5 -> # MONGO_MAX_POOL_SIZE=5
If the default is 5 but it was set on purpose to unlimited -> Either change the default to unlimited or change the example to use 5. In both cases put the value as a comment into the exmaple file.