feat: add support for optional credit class image

[blushi]

Description

ref: regen-network/regen-registry#1428

It also removes some unnecessary @typess : https://github.com/regen-network/regen-registry-standards/pull/56/commits/2872e5e755f1113615efbdcdc40890f9cec1c4b0 The impacted metadata also got updated on the prod database (their IRIs remaining the same since those changes are only format related changes and don't have any impact on the resulting canonized data)

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[blushi]

@wgwz could you help with the docker build issue: https://github.com/regen-network/regen-registry-standards/actions/runs/5276167983/jobs/9542523640?pr=56? thanks!

[wgwz]

@blushi no prob, it was just a new release of a debian docker image that we automatically upgraded to causing the issue. i pushed a commit to pin us to the debian release that we were using previously (bullseye).