Copy header value Traefik plugin

Traefik plugin that copies HTTP header value with format key1=value1; key2=value2 into a new header. Motivation for this plugin is to be able to extract a particular key's value from Cookie header. However, it can be adapted for other purposes taking into account this plugin's limitations, e.g. only a single key's value can be copied.

Configuration

Traefik static configuration for plugin:

...
experimental:
  plugins:
    copy-header-value:
      moduleName: github.com/argyle-engineering/copy-header-value-traefik-plugin
      version: v1.0.0

Plugin is then configured as a route middleware

apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
  name: copy-header-value
spec:
  plugin:
    copy-header-value:
      from: "Cookie"
      pairSeparator: ";"
      keyValueSeparator: "="
      key: "id"
      to: "Authorization"
      prefix: "Bearer "
      overwrite: false

In this example, when there is Cookie header, value identified by the id key will be moved into Authorization header with Bearer as a value prefix. In case Authorization header already exists, overwrite controls whether it will be overwritten with the value extracted from Cookie header.