Renaming sipity_header_id to header_id
Adding ezid-client

$ bundle
@WIP Adding Ezid::Client
Preliminary commit for DOI Creation
Expanding on the DOI Creation Request Job
Updating secrets
Dependency injection for DoiCreationRequest
Teasing apart DoiCreationRequestJob
Appeasing Rubocop
Adding Repository to DoiCreationRequest
Adding TODO items

[skip ci]
Adding comments

[skip ci]
Adding #permanent_uri_for_header_id
Introducing a metadata builder
Rudimentary metadata builder for DOI
Appeasing Rubocop