Add option to override image validation

[joaodubas]

Expose the image validation process to the end user so that custom images can be used without re-implementing all the container specifications.

The image validation is controlled by a regular expression set in the check_image on the Testcontainers.Container module and accessible through the method with_check_image/2. All the specialized containers are adjusted to provide a default value for this check and allow an override.

For example, instead of using the redis image, it's possible to use the valkey alternative without major changes:

{:ok, _} = Testcontainers.start_link()
config = Testcontainers.RedisContainer.new() |> Testcontainers.RedisContainer.with_image("valkey/valkey:7.2.5-bookworm") |> Testcontainers.with_check_image(~r/.*\bvalkey\b.*/)
{:ok, container} = Testcontainers.start_container(config)

Solves issue #106.

[jarlah]

need to think about this. I am not sure if it's smart to continue with starts_with check on string.

Two suggestions:

1. use a regex instead of supplying the image as a string. This could be made possible/userfriendly by making an "overloaded" versions of with_default_image that converts the binary input to a regex (or fails if it's not a valid regex). This way, you can supply both a string or a regex.
2. assume that when default_image is not supplied there is no image validation. And replace check_image? with a check_image function, with an accompanying method with_check_image that checks if the parameter is a function that takes the appropriate parameters to be used in the validation of the image. Cutting out the need for the extra boolean field.

Let me sleep on it, and do make yourself some opinions on this also. I might not have the best ideas around, but I'm aiming for future proofing and avoiding quick fixes ;)

[joaodubas]

I agree that adding two new fields to control the validations seems strange. We can pass an optional function that validates the image's compliance. Something along the lines of:

defmodule Testcontainers.Container do

  defstruct [..., check_image: fn _image -> true end]

  def with_check_image(%__MODULE__{} = config, check_image) when is_function(check_image) do
    %__MODULE__{config | check_image: check_image}
  end

  def check_image(%__MODULE__{} = config) do
    if config.check_image.(config.image) do
       {:ok, config}
    else
      {:error, "Unexpected image #{config.image}. If this is a valid image, provide a broader `check_image` function to the container configuration."}
    end
  end

I'll play on more generic solutions and seek inspiration on the other implementations of Testcontainers.

[joaodubas]

I re-implemented the validation using regular expressions; overall, it seems a more straightforward solution. But I don't know if we should implement a parser for the image and try to extract the register/user/image/tag data and use this information.

[jarlah]

Nice work. Thanks for the contribution. This is backwards compatible, so i will make a patch release with this change. The commits will be squashed when merged fyi, unless you rebase and squash the commits yourself.

[joaodubas]

Nice work. Thanks for the contribution. This is backwards compatible, so i will make a patch release with this change. The commits will be squashed when merged fyi, unless you rebase and squash the commits yourself.

Thanks for all the assistance and review.