gptel-bedrock: Plumb request-params all the way through

[brickZA]

Commit 3d5fecc added partial support for passing request-params through to the AWS Bedrock backend. This commit plumbs it all the way through to gptel--request-data

I tested it with the following config:

  (setq gptel-model   'claude-3-7-sonnet-20250219 ;'claude-sonnet-4-20250514
        gptel-backend
        (gptel-make-bedrock "AWS"
          ;; optionally enable streaming
          :stream t
          :region "eu-west-1"
          ;; subset of gptel--bedrock-models
          :models '(claude-sonnet-4-20250514 claude-3-7-sonnet-20250219)
          ;; Model region for cross-region inference profiles. Required for models such
          ;; as Claude without on-demand throughput support. One of 'apac, 'eu or 'us.
          ;; https://docs.aws.amazon.com/bedrock/latest/userguide/inference-profiles-use.html
          :request-params '(:additionalModelRequestFields (:thinking (:type "enabled" :budget_tokens 2048))
                      :inferenceConfig (:max_tokens 4096))
          :model-region 'eu)

It does not look like the Bedrock parser understands thinking yet, but I can confirm that it worked by looking at the debug output. We note the added fields in the request body:

{
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "text": "Testing!"
        }
      ]
    }
  ],
  "inferenceConfig": {
    "max_tokens": 4096
  },
  "system": [
    {
      "text": "You are a large language model living in Emacs and a helpful assistant. Respond concisely."
    }
  ],
  "temperature": 1.0,
  "additionalModelRequestFields": {
    "thinking": {
      "type": "enabled",
      "budget_tokens": 2048
    }
  }
}

and the bedrock response now contains reasoningContent events (after running through the strings command):

event{"contentBlockIndex":0,"delta":{"reasoningContent":{"text":"The"}},"p":"abcdef"}
...
event{"contentBlockIndex":0,"delta":{"reasoningContent":{"text":" user is just saying \""}},"p":"abcdefghijklmnopqrstuvw"}
...
event{"contentBlockIndex":0,"delta":{"reasoningContent":{"text":"Testing!\". This looks like they"}},"p":"abcdefghijkl"}
...

[karthink]

@brickZA Thanks for the PR!

[brickZA]

No problem, just helping myself :)