* s3api: load document-style policies from the advanced IAM config
The advanced IAM file doubles as the S3 identity config when only
-s3.iam.config is given. protojson drops its "document" field, so every
policy landed with empty content and warned "skipping invalid policy" on
each reload. Worse, if the same file also declares identities the empty
content sticks in the policy map and fails the whole runtime policy sync
into the IAM manager, so policies created later never reach it.
* iam: skip an unparsable policy instead of failing the whole runtime sync
One policy the engine cannot parse aborted SyncRuntimePolicies before it
touched anything, so every other policy stayed unsynced and the engine
kept serving whatever it last held.
* s3api: reject a non-role RoleArn in AssumeRole as a bad request
arn:aws:iam:::user/name can never resolve to a role, but the handler ran
it through the trust-policy check and answered "not authorized to assume
role", pointing the caller at a permission problem they do not have.
* s3api: build the policy content before touching the entry
Deleting "document" up front meant a marshal failure left the policy with
neither field, so a later rewrite would emit it with no definition at all.
* iam: pin the fail-closed handling of an unparsable policy
Say in the comment that dropping it from the desired set deletes it from
the engine on purpose, and cover it with a test.
* s3api: widen the non-role RoleArn test to canonical ARN shapes
The reported ARN omits the account id; a user ARN that carries one, and a
non-principal ARN, must be rejected the same way.
see https://blog.aqwari.net/xml-schema-go/
1. go get aqwari.net/xml/cmd/xsdgen
2. Add EncodingType element for ListBucketResult in AmazonS3.xsd
3. xsdgen -o s3api_xsd_generated.go -pkg s3api AmazonS3.xsd
4. Remove empty Grantee struct in s3api_xsd_generated.go
5. Remove xmlns: sed s'/http:\/\/s3.amazonaws.com\/doc\/2006-03-01\/\ //' s3api_xsd_generated.go