Change dhparam positional args to be inherited vars, standardize naming

[jessejoe]

PR #913 added DHPARAM_GENERATION as a positional argument to generate-dhparam.sh. However, since it was the second positional argument,DHPARAM_BITS would also have to be defined or DHPARAM_GENERATION would be read into DHPARAM_BITS. This changes the arguments to be inherited variables which do not depend on order, just declaration.

Also change instances of GENERATE_DHPARAM to DHPARAM_GENERATION since it's unnecessary to have another variable. I think GENERATE_DHPARAM is actually a better name (verb vs. noun), but DHPARAM_GENERATION is already defined and may break someone if changed.

Addresses #913 (comment)

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Behavior before:

$ docker run -it --rm -e "DHPARAM_GENERATION=false" testing /bin/bash
WARNING: /etc/nginx/dhparam/dhparam.pem was not found. A pre-generated dhparam.pem will be used for now while a new one
is being generated in the background.  Once the new dhparam.pem is in place, nginx will be reloaded.
dhparam: Can't parse "false" as a number

Behavior after:

$ docker run --rm -e "DHPARAM_GENERATION=false" testing /bin/bash
Skipping Diffie-Hellman parameters generation and Ignoring pre-generated dhparam.pem

[kamermans]

[CC @jwilder] this looks good to me, thanks @jessejoe!

[buchdag]

@jwilder this is a required fix, could you merge please ?

[joren485]

I believe with this change

# Generate dhparam file if required
# Note: if $DHPARAM_BITS is not defined, generate-dhparam.sh will use 2048 as a default
# Note2: if $DHPARAM_GENERATION is set to false in environment variable, dh param generator will skip completely
/app/generate-dhparam.sh $DHPARAM_BITS $DHPARAM_GENERATION

should be changed to

# Generate dhparam file if required
/app/generate-dhparam.sh

in entrypoint.sh.

[buchdag]

• rebased on main
• fixed merge conflict
• included @joren485 suggestion
• did a bit of linting on the shell scripts while we're at it