Backport of docs: Add complete auth method payloads into release/1.15.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #18849 to be assessed for backporting due to the inclusion of the label backport/1.15.

The below text is copied from the body of the original PR.

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Description

This commit modifies the example payloads for various auth methods to remove 'other fields' and instead use complete example payloads.

This helps readers clearly understand how the payloads should be constructed for the /v1/acl/auth-method API endpoint.

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

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Overview of commits

• 30b6777

[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR

[hc-github-team-consul-core]

🤔 This PR has changes in the website/ directory but does not have a type/docs-cherrypick label. If the changes are for the next version, this can be ignored. If they are updates to current docs, attach the label to auto cherrypick to the stable-website branch after merging.