chore(docs): create ADR for client-side routing

[taymoor89]

Summary

This PR add an ADR for client-side routing so other apps can add routing based on the same principals.

Changes Made

• Created an ADR in docs

Related Issues

• [Task](Juno): ADR for Tanstack router usage, common URL patterns (for pages, Panel, Modal, state), testing #1022

Screenshots (if applicable)

Testing Instructions

1. pnpm i
2. pnpm TASK

Checklist

• I have performed a self-review of my code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have made corresponding changes to the documentation (if applicable).
• My changes generate no new warnings or errors.
• I have created a changeset for my changes.

PR Manifesto

Review the PR Manifesto for best practises.

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[andypf]

👍

[hodanoori]

Thanks for preparing this ADR

[barsukov]

why do we need our custom encoding, url-state-provider and do not use default SearchParams from Tanstack.
What is the use case for that?

[taymoor89]

Recently, we introduced v2 of the encoding/decoding utilities in url-state-provider. These utilities are essentially thin wrappers around the query-string library (which, by the way, is also referenced in the official TanStack Router docs). By default, TanStack uses JSON.stringify for URL serialization.

You might wonder: If we can use query-string directly with TanStack Router, why expose it through url-state-provider?

Here are the key reasons:

1. Consistent flat structure: We want application developers to persist state to the URL in a flat format—not deeply nested. Arrays of primitive values are allowed, but complex nested collections are not.
2. Improved readability: The query-string library provides a more human-readable URL format compared to the default JSON.stringify output. For example we can put arrays strings in a nicely comma separated form in the URL which is human readable(filters are a very good use-case of it).
3. Centralized control: Exposing the utility through url-state-provider lets us control the query-string version and apply sensible, consistent defaults across the app.

[edda]

@taymoor89 I like the detailed explanation. I would propose to add this (maybe as a footnote) to the ADR itself so it doesn't get lost

[ArtieReus]

lgtm

[hodanoori]

lgtm

[edda]

Thank you! I like it!

Two things I would propose:

1. add the info form your comment with the justification for the encode/decode utility to the ADR itself. I think it's very valuable additional information that helps understand the decision. Also a simple example of what encode and decode does could help
2. Section 5. Route Definitions and UI State: a couple of examples would help understand this better, imo. So give an example for one or two routes coming out of the file-based routing, then give an example how they would change with an opened panel or modal.