Elixir Pipeline for Customer Feedback Processing

Problem Description

A SaaS company receives customer feedback submissions through a web form. Each submission is a map containing a customer ID, a rating (integer 1–5), a comment (string), and a timestamp (ISO 8601 string). The data arrives as a list of raw maps from a database query. Before being stored in the analytics system, each submission needs to go through several transformation steps: parse and validate the timestamp, reject submissions with invalid ratings, normalize the comment text (trim whitespace, lowercase), and finally compute a per-rating breakdown showing how many submissions fall into each score bucket.

A backend engineer wants to implement this as a clean functional pipeline in Elixir. The input is a list of maps (each representing one submission). The output is a map of rating counts plus the count of rejected submissions.

There is no existing code. Design and implement the solution in Elixir.

Output Specification

Produce a file named feedback_pipeline.ex containing the full Elixir module and implementation. Also produce a file named pipeline_analysis.md documenting the transformation analysis: the data flow, step breakdown, implementation explanation, and how errors propagate through the pipeline.

The final output of the pipeline function should be a map like:

%{
  processed: 87,
  rejected: 5,
  rating_counts: %{1 => 3, 2 => 10, 3 => 22, 4 => 31, 5 => 21}
}