Improvements to debug logging and CORS handling

[alexcreasy]

Description

Adds some improvements to debug logging:

• Less boilerplate and easier to use code style that follows the slog API
• Logging of headers with redaction of sensitive headers
• Logs static resource requests

Improves CORS handling, making the calls more efficient

How Has This Been Tested?

Run with locally on kind, fire off some curl requests and analyse what comes out, try something like this:

curl -i -H "Authorization: top-secret-token-tell-noone" -H "kubeflow-userid: user@example.com" -X POST "http://localhost:4000/api/v1/model_registry/model-registry/registered_models?namespace=kubeflow" \
     -H "Content-Type: application/json" \
     -d '{ "data": {
  "customProperties": {
    "my-label9": {
      "metadataType": "MetadataStringValue",
      "string_value": "val"
    }
  },
  "description": "bella description",
  "externalId": "9927",
  "name": "bella",
  "owner": "eder",
  "state": "LIVE"
}}'

Verify the Authorisation header is redacted.

Merge criteria:

• All the commits have been signed-off (To pass the DCO check)

• The commits have meaningful messages; the author will squash them after approval or in case of manual merges will ask to merge with squash.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work.
• Code changes follow the kubeflow contribution guidelines.

If you have UI changes

• The developer has added tests or explained why testing cannot be added.
• Included any necessary screenshots or gifs if it was a UI change.
• Verify that UI/UX changes conform the UX guidelines for Kubeflow.

[google-oss-prow]

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[alexcreasy]

@lucferbux @ederign any chance of a review when you get a moment?

[ederign]

I'll look at it today! sorry for the delay!

[ederign]

Thank you @alexcreasy ! I did a small sanity check locally also with web app.

[ederign]

/lgtm