Allow access to secrets for external contributors

[aguschin]

Using the changes from iterative/cml#574

[aguschin]

@0x2b3bfa0 could you please TAL?

[0x2b3bfa0]

Note that the external environment should be configured to require @iterative/mlem as reviewer to approve every run.

[0x2b3bfa0]

E.g. visit https://github.com/iterative/mlem/settings/environments/new and create a new environment named external with the following settings:

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[0x2b3bfa0]

Looks good to me, although still needs an administrator to configure the external environment before merging.

[aguschin]

Thanks @0x2b3bfa0! I've created an environment. Do I need to copy secrets from Repository secrets to Environment secrets now? Or it will work with all secrets listed in Repository secrets only?

[aguschin]

As per this page I found repository secrets should be available in the environment. Merging :)
https://dev.to/n3wt0n/how-secrets-work-in-github-and-how-to-manage-them-p4o