feat(endpoint): add renderUrl method to Endpoint (#3162)

[987Nabil]

Summary

Adds Endpoint.renderUrl methods to render the URL template including both path and query parameter placeholders.

Usage

val ep = Endpoint(Method.GET / "api" / "users" / int("userId"))
  .query[Int](HttpCodec.query[Int]("page"))
  .query[Int](HttpCodec.query[Int]("limit"))

ep.renderUrl           // "/api/users/{userId}?page={page}&limit={limit}"
ep.renderUrl("/v1")    // "/v1/api/users/{userId}?page={page}&limit={limit}"

API

• def renderUrl: String — renders path + query params
• def renderUrl(basePath: String): String — with base path prefix

Query parameter names are extracted from the codec's record fields. Path parameters use the existing PathCodec.render format.

Closes #3162

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[Copilot]

Pull request overview

Adds a convenience API on Endpoint to render a URL template string (path + query placeholders), intended for documentation / client generation / debugging use cases (per #3162).

Changes:

• Introduces Endpoint.renderUrl: String to render the endpoint path template plus query parameter placeholders.
• Introduces Endpoint.renderUrl(basePath: String): String to prefix a base path to the rendered template.
• Adds a private queryParamNames extractor that walks the endpoint’s HttpCodec input to find query parameter names.

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[Copilot]

renderUrl / renderUrl(basePath) introduce new public behavior but there are no accompanying tests to lock in rendering for common cases (no query params, multiple individual query params, case-class query params, optional query params, fallbacks/alternatives, and basePath with/without trailing slash). Adding a focused spec would help prevent regressions and clarify intended output formatting.

[Copilot]

HttpCodec.Fallback is currently handled by concatenating query param names from both sides (loop(left) ++ loop(right)), which can render duplicated placeholders (e.g. query(Int("userId") | query(String("userId")) would produce userId={userId}&userId={userId}) and can also imply that alternative query params are simultaneously present. Consider mirroring PathCodec.render behavior by taking only the left branch, or otherwise de-duplicating/encoding the fact that params are alternatives so the rendered URL is not misleading.

Suggested change

	case HttpCodec.Fallback(left, right, _, _) => loop(left) ++ loop(right)
	case HttpCodec.Fallback(left, right, _, _) => loop(left)

[Copilot]

q.codec.recordFields can contain null/empty field names when the query codec is derived without an explicit name (e.g. HttpCodec.query[Int] uses queryFromSchema(..., name = null) for primitives). In that case renderUrl will emit null={null}. It would be safer to filter out null/blank names and either omit them or fall back to a stable placeholder name.

Suggested change

	if (fields.nonEmpty) fields.map(_.toString)
	val validFields = fields.filter {
	case null => false
	case name => name.toString.trim.nonEmpty
	}
	if (validFields.nonEmpty) validFields.map(_.toString)

[Copilot]

renderUrl(basePath) strips exactly one trailing /, but other URL-building APIs in this type (e.g. url(basePath, values)) appear to do a raw concatenation. This difference can be surprising for callers and makes base-path semantics inconsistent. Consider aligning behavior (either normalize in both places or neither) and/or documenting what forms of basePath are supported (leading slash required? trailing slash ignored?).