feat: Add ability to expire cached credentials

[DanielMe]

I tried using avante with the Bedrock provider and I found it quite nice to obtain the credenitals using the command as api_key_name convention: It allows a config such as the following to get the credentials string from an AWS profile:

  opts = {
    provider = "bedrock",
    -- I'm not sure if auto suggestions are even active but if I do not set this to bedrock, I will still be prompted
    -- for a anthropic key for no reason
    auto_suggestions_provider = "bedrock",
    bedrock = {
      model = "anthropic.claude-3-5-sonnet-20241022-v2:0",
      api_key_name = { "sh", "-c", "REGION=$(aws configure get region --profile bedrock) && aws configure export-credentials --profile bedrock | jq -r --arg region \"$REGION\" '[.AccessKeyId, .SecretAccessKey, $region, .SessionToken] | join(\",\")'"},
    },
  },

The bedrock aws profile gives me short-lived credentials which are refreshed using the credentials_process using SSO. (https://docs.aws.amazon.com/cli/v1/userguide/cli-configure-sourcing-external.html).

The only problem with this setup is that Avante caches these credentials and I have to restart nvim once they expire.

My proposal in this PR is to add an optional parameter reevaluate_api_key_after which invalidates the credenitals cache after a set number of seconds.

Note that there are two different caches that need to be invalidated, one in providers/init.lua and one in environment.lua. My idea was to add the expiry to one of them and a force invalidation flag to the other. Note furthermore, that the command execution in environment.lua is async which is fine for startup where we do not want to block on this evaluation - however when we invalidate the credentials, we actually want to wait for the credentials to be available because the old credentials are likely no longer available.

[Qkessler]

Thanks so much for this! Just pulled the PR and was able to work with the README instructions without issues! Like the proposed approach. As a step forward, the bedrock integration could be abstracted further to work with either:

1. The current static credentials approach, to avoid a breaking change for current users.
2. Abstract the integration to allow the user to configure a profile that auto-refreshes. Avante.nvim would then take the profile and configure itself to get up-to-date credentials, modifying the cache.

Thoughts?

cc @yetone for input on the vision for Bedrock support.

[yetone]

hello, can you help resolve the code conflicts?

[DanielMe]

Hey, apologies for the delay, I resolved the merge conflicts and validated that it did not break my nvim config

[github-actions[bot]]

This PR is stale because it has been open 14 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[yetone]

hello, can you help me to fix the ci failed and code conflicts?

[github-actions[bot]]

This PR is stale because it has been open 14 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[yetone]

Sorry, due to too many conflicts with this one, I might create a new PR referencing your implementation to complete this task. I'm very sorry.