feat: Add http method into session.MatchContext

[corrideat]

Related issue

#625

Proposed changes

The HTTP Request method becomes available in MatchContext, so that it may be used in templates.

Checklist

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[robbietree8]

Does the docker image containing this patch published to docker hub?
Currently, the latest docker tag points to v0.38.9.

@aeneasr

[aeneasr]

We have some issues with the CI in Ory Oathkeeper but I probably won't have time this week to look into it. Any contribs welcomed!