feat: CLI argument for custom registry URL was introduced

[misterku]

What does this do / why do we need it?

Sometimes it is necessary to override default terraform registry with other registry. This PR introduces new CLI argument to do it.

How this PR fixes the problem?

PR introduces argument custom-terraform-registry-url (or -u) which can override default terraform registry URL and use provided instead.

Check lists

• Test passed
• Coding style (indentation, etc)

[Junkern]

Thanks a lot for the contribution and great idea!

I am not so happy about passing the custom-terraform-registry-url through all the different methods, though. IMHO it should be set as a new value in the app.Config. Default value should be the normal registry URL and when the flag is set, a new method setTerraformRegistryUrl is called which sets the app.Config.TerraformRegistryUrl to its new value. The getProviderData simply accesses app.Config.TerraformRegistryUrl

What do you think about that?

[coveralls]

Pull Request Test Coverage Report for Build 3230244250

• 3 of 10 (30.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.7%) to 64.128%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/app/app.go	1	4	25.0%
internal/app/install.go	2	6	33.33%

Totals
Change from base Build 3119110509:	-0.7%
Covered Lines:	320
Relevant Lines:	499

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💛 - Coveralls

[misterku]

Thank you for the feedback. Yes, I agree that using app.Config would be better. I've updated the PR with changes based on your suggestions.