Repo HEAD export should be allowed by Repo Authors

[snyaggarwal]

Problem:
Currently, Repo HEAD can only be exported by OCL Staff Users.

Solution:
Allow repo version HEAD to be exported by Repo authors.

[filiperochalopes]

Not just authors I think. Org member as well @jamlung-ri

[snyaggarwal]

@filiperochalopes Org members are the authors/editors of the Repo

[snyaggarwal]

@filiperochalopes Raised PR OpenConceptLab/oclapi2#880