Add metadata and tags to mc find

[klauspost]

Description

Add metadata and tag search.

In both cases a MinIO sever must be on the backend. Tags and --versions requires the latest release.

This is required for fixing unmarshal: minio/minio-go#1795

Motivation and Context

Examples

λ mc find -json -tags="key=v*" myminio/testbucket/
{
 "status": "success",
 "type": "",
 "lastModified": "2023-01-05T10:26:13.12+01:00",
 "size": 712001,
 "key": "myminio/testbucket/out.csv",
 "etag": "",
 "metadata": {
  "X-Amz-Server-Side-Encryption": "aws:kms",
  "content-type": "text/csv"
 },
 "tags": {
  "key": "value",
  "key2": "",
  "key3": "else"
 }
}

Metadata:

λ go build&&mc find -json -metadata="content-type=text/csv" myminio/testbucket/
{
 "status": "success",
 "type": "",
 "lastModified": "2023-01-19T17:38:43.803+01:00",
 "size": 342934,
 "key": "myminio/testbucket/go2/src/cmd/go/internal/modfetch/zip_sum_test/testdata/zip_sums.csv",
 "etag": "",
 "metadata": {
  "X-Amz-Server-Side-Encryption": "aws:kms",
  "content-type": "text/csv"
 }
}
{
 "status": "success",
 "type": "",
 "lastModified": "2023-01-19T17:41:03.011+01:00",
 "size": 342934,
 "key": "myminio/testbucket/go3/src/cmd/go/internal/modfetch/zip_sum_test/testdata/zip_sums.csv",
 "etag": "",
 "metadata": {
  "X-Amz-Server-Side-Encryption": "aws:kms",
  "content-type": "text/csv"
 }
}

If a value is empty -metadata="X-Amz-Server-Side-Encryption=" it must either not exist or have an empty value.

Multiple tags or metadata fields can be queried, eg -metadata="content-type=text/csv" -metadata="X-Amz-Server-Side-Encryption=.". In that case all of them must exist.

Regex is Go RE2 syntax.

How to test this PR?

See examples above.

Types of changes

• New feature (non-breaking change which adds functionality)

[krisis]

Great stuff! PR looks good. Need to update go.mod to use latest minio-go.

[klauspost]

Merged...