Rule Request: [doc_pattern]. required_pattern for a doc comment

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New rule request

I've been trying to create a custom rule to force a pattern in documenting functions, specifically tests functions.
I want to force a multiline format for the tests as follows

class MyTests: XCTestCase {

    /// ### Given
    /// a
    /// ### When
    /// b
    /// ### Then
    /// c
    func testExample() throws {
    }

I've been trying to achieve this required pattern rule using a custom rule but I could not succeed, I don't even know if it would be possible.
I think a required pattern rule for functions can be beneficial:

• to enforce doc styling,
• to ease automatic parsing of doc for other tools to use.

The format of the rule could be inspired by the file_header rule

doc_pattern:
  required_pattern:
  included:
  name:
  match_kinds:
  message:
  severity:

The rule should be opt-in.

No implementation file or test is identified in the issue. Start by reviewing SwiftLint’s existing file_header rule and custom-rule capabilities, then define the opt-in configuration using the requested fields and add coverage for the multiline function-documentation pattern.