functions: feature: add resource, and data source for functions and namespaces

[KylePeterDavies]

Is your feature request related to a problem? Please describe.

I want to be able to create DigitalOcean Functions with Terraform.

Describe the solution you'd like

I would like DigitalOcean to implement Resources and Data Sources for Digital Ocean Functions, and Digital Ocean Function Namespaces.

doctl serverless namespace --create --label namespace --region ams3

resource "digitalocean_function_namespace" "namespace" {
  name   = "namespace" # or label to keep parity with the cli
  region = "ams3" 
}

doctl serverless deploy name

resource "digitalocean_function" "function" {
  package = "discord"
  function_name = "webhook"
  entry_point = ""
  runtime = "go:1.20"
  filename = "function.go"
  source_code_hash  = # some hash code
}

Describe alternatives you've considered

I have considered using the project.yml, But, I would like to implement with established tools, and practices.

Additional context

Please let me know if you are open to code contributions.

See AWS Lambda Function and GCP Cloud Function