Fixing Hubbard formulation

[t-reents]

Addresses #1220

@bastonero I applied the fix as discussed in the issue. Moreover, I also added "ALPHA" to the supported values. Please have a look whether my understanding/logic for the dudarev formulation was correct.

One additional aspect:

I was wondering, do we actually need this check here:

aiida-quantumespresso/src/aiida_quantumespresso/utils/hubbard.py

Lines 65 to 66 in 0f4318b

	if hubbard.formulation not in ['dudarev', 'liechtenstein']:
	raise ValueError(f'Hubbard formulation {hubbard.formulation} is not implemented.')

Isn't this automatically validated in:

aiida-quantumespresso/src/aiida_quantumespresso/common/hubbard.py

Lines 151 to 152 in 0f4318b

	formulation: Literal['dudarev', 'liechtenstein'] = 'dudarev'
	"""Hubbard formulation used. Allowed values are: 'dudarev', `liechtenstein`."""

[bastonero]

thanks a lot @t-reents. would you be a lamb and add a little test when actually using the liechtenstein "keyword"?

[bastonero]

could you also add J0? https://www.quantum-espresso.org/Doc/INPUT_PW.html#id329
this should be the one used in liechtensteain

[bastonero]

re the ValueError: yeah, in principle it can be removed the check. it was put there in case we wanted to have other formulations (don't even know if there are so many others...), so that we didn't need to modify. but agreed it is currently unnecessary