Stop requiring gitaly storage with name "default"
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### Problem to solve
Currently in my installation i have got multiple storages with gitaly[1-n] names that have similar configurations and they are located on VMs named same way. But suddenly I need forced to create gitaly named default cause it's currently required.
Actually I don't understand why default storage is required.
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### Intended users
Selfhosted gitlab admins
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### Further details
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### Proposal
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### Documentation
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### Testing
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### What does success look like, and how can we measure that?
Gitalies naming is fully controlled by user
### What is the type of buyer?
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### Links / references
issue