workflow run namespace: property for file checksums

[simleo]

As discussed at the WRROC meeting

[simleo]

E.g. like https://schema.org/sha256, but we also need other popular ones

[stain]

see also
https://datatracker.ietf.org/doc/html/rfc6920

From schemaorg/schemaorg#3162

rfc6920 Naming things with hashes that establishes ways to identify checksum algorithms and representing their checksums as URIs.

Example:

ni:///sha-256;f4OxZX_x_FO5LcGBSKHWXfwtSx-j1ncoSt3SABJtkGk 

identifies anything with the sha256 with the given base64-encoded checksum

alternatively in hex/human readable:

nih:sha-256;7f83b1657ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069

(rfc6920 also specifies how to deal with truncation)

See rfc6920 register for more algorithms.

Combined with arcp URIs this is suggested already by RO-Crate for Establishing a base URI inside a ZIP file.