Adds openalex client as a default client

[nadolskit]

Summary of Changes

• Adds new default client "OpenAlex"
  • Externalizes BIB_MAPPING out of crossref client for both clients to use
  • Misc utils to support OpenAlex response data into our infrastructure
• New cassettes

[whitead]

Got this error playing with the branch:

File ~/repos/paper-qa/paperqa/clients/openalex.py:155, in parse_openalex_to_doc_details(message)
    [147](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:147) authors = [reformat_name(author) for author in authors]
    [148](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:148) sanitized_authors = [
    [149](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:149)     mutate_acute_accents(text=author, replace=True) for author in authors
    [150](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:150) ]
    [152](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:152) publisher = (
    [153](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:153)     message.get("primary_location", {})
    [154](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:154)     .get("source", {})
--> [155](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:155)     .get("host_organization_name")
    [156](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:156) )
    [157](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:157) journal = message.get("primary_location", {}).get("source", {}).get("display_name")
    [159](https://file+.vscode-resource.vscode-cdn.net/Users/andrewwhite/Dropbox/SDB/peptides/~/repos/paper-qa/paperqa/clients/openalex.py:159) best_oa_location = message.get("best_oa_location")

AttributeError: 'NoneType' object has no attribute 'get'

[nadolskit]

@whitead odd, I thought that defaulting to empty objects would prevent that I'll look into it.