* iam: bind CreateServiceAccount target to caller in AuthorizeIamAction
A non-admin holding iam:CreateServiceAccount could pass an arbitrary
ParentUser and mint a service account for any identity, inheriting that
identity permissions. Add a self-target category so a granted non-admin
may only target their own identity; admins remain unrestricted.
* iam: authorize CreateServiceAccount against its ParentUser target
AuthIamManagement passed UserName as the authorization target for every
action, so CreateServiceAccount was authorized with an empty target and
the self-target binding never saw the caller-supplied ParentUser. Pass
ParentUser for that action so the binding takes effect on the live path.
* iam: test CreateServiceAccount binds target to caller
Regression test: a non-admin holding iam:CreateServiceAccount may target
itself but is denied targeting another identity; admins remain
unrestricted.
* iam: authorize CreateServiceAccount against ParentUser on the S3 port
UnifiedPostHandler passed UserName as the authorization target for every
IAM action, so CreateServiceAccount was authorized with an empty target
on the S3-port route and the self-target binding never saw the caller
ParentUser. Extract iamTargetUserName (ParentUser for CreateServiceAccount,
UserName otherwise) and use it from both IAM dispatch surfaces so the
binding applies on the live S3-port path as well as the standalone iam
server.
* iam: test CreateServiceAccount ParentUser binding on the S3 port
End-to-end regression test through UnifiedPostHandler: a non-admin
holding iam:CreateServiceAccount is denied (403) when targeting another
identity and passes authorization when targeting itself.
* s3: keep a non-S3 action out of the request-shape resolver
ResolveS3Action reads the request shape before it looks at the base action, so
an iam: or sts: action on a request that happens to carry an S3 query parameter
came back as the S3 action for that parameter. An action that already names its
service is resolved; there is no S3 request shape to read for it.
* iam: authorize the standalone IAM server's actions as IAM, not as S3
The standalone `weed iam` server wrapped its single POST / route in the generic
S3 Auth middleware with ACTION_ADMIN. The route has no {bucket}, so the check
ran with an empty bucket and resolved to a coarse S3 action rather than the IAM
one. The embedded IAM surface checks iam:<Action>; the standalone one was never
updated to match.
Both now go through one authorization function, so they cannot drift apart
again. It also rejects the anonymous identity, which has no user of its own to
run a self-service action against, and reads UserName from the body only, where
the handlers read it from.
Chris Lu