fix: jfrog oauth username extraction from oauth jwt token (#539)

## Description

Add username extraction from jfrog JWT OAuth token with fallback to
coder username.
<!-- Briefly describe what this PR does and why -->

## Type of Change

- [ ] New module
- [ ] New template
- [X] Bug fix
- [ ] Feature/enhancement
- [ ] Documentation
- [ ] Other

## Module Information

<!-- Delete this section if not applicable -->

**Path:** `registry/coder/modules/jfrog-oauth`  
**New version:** `v1.2.2`  
**Breaking change:** [ ] Yes [X] No

## Template Information

<!-- Delete this section if not applicable -->

**Path:** `registry/[namespace]/templates/[template-name]`

## Testing & Validation

- [X] Tests pass (`bun test`)
- [X] Code formatted (`bun fmt`)
- [X] Changes tested locally

## Related Issues

<!-- Link related issues or write "None" if not applicable -->

registry/coder/modules/jfrog-oauth/README.md

@@ -16,7 +16,7 @@ Install the JF CLI and authenticate package managers with Artifactory using OAut
 module "jfrog" {
   count          = data.coder_workspace.me.start_count
   source         = "registry.coder.com/coder/jfrog-oauth/coder"
-  version        = "1.2.1"
+  version        = "1.2.2"
   agent_id       = coder_agent.example.id
   jfrog_url      = "https://example.jfrog.io"
   username_field = "username" # If you are using GitHub to login to both Coder and Artifactory, use username_field = "username"
@@ -39,6 +39,15 @@ module "jfrog" {
 
 This module is usable by JFrog self-hosted (on-premises) Artifactory as it requires configuring a custom integration. This integration benefits from Coder's [external-auth](https://coder.com/docs/v2/latest/admin/external-auth) feature and allows each user to authenticate with Artifactory using an OAuth flow and issues user-scoped tokens to each user. For configuration instructions, see this [guide](https://coder.com/docs/v2/latest/guides/artifactory-integration#jfrog-oauth) on the Coder documentation.
 
+## Username Handling
+
+The module automatically extracts your JFrog username directly from the OAuth token's JWT payload. This preserves special characters like dots (`.`), hyphens (`-`), and accented characters that Coder normalizes in usernames.
+
+**Priority order:**
+
+1. **JWT extraction** (default) - Extracts username from OAuth token, preserving special characters
+2. **Fallback to `username_field`** - If JWT extraction fails, uses Coder username or email
+
 ## Examples
 
 Configure the Python pip package manager to fetch packages from Artifactory while mapping the Coder email to the Artifactory username.
@@ -47,7 +56,7 @@ Configure the Python pip package manager to fetch packages from Artifactory whil
 module "jfrog" {
   count          = data.coder_workspace.me.start_count
   source         = "registry.coder.com/coder/jfrog-oauth/coder"
-  version        = "1.2.1"
+  version        = "1.2.2"
   agent_id       = coder_agent.example.id
   jfrog_url      = "https://example.jfrog.io"
   username_field = "email"
@@ -76,7 +85,7 @@ The [JFrog extension](https://open-vsx.org/extension/JFrog/jfrog-vscode-extensio
 module "jfrog" {
   count                 = data.coder_workspace.me.start_count
   source                = "registry.coder.com/coder/jfrog-oauth/coder"
-  version               = "1.2.1"
+  version               = "1.2.2"
   agent_id              = coder_agent.example.id
   jfrog_url             = "https://example.jfrog.io"
   username_field        = "username" # If you are using GitHub to login to both Coder and Artifactory, use username_field = "username"

registry/coder/modules/jfrog-oauth/main.tf

@@ -76,8 +76,27 @@ variable "package_managers" {
 }
 
 locals {
-  # The username field to use for artifactory
-  username   = var.username_field == "email" ? data.coder_workspace_owner.me.email : data.coder_workspace_owner.me.name
+  jwt_parts   = try(split(".", data.coder_external_auth.jfrog.access_token), [])
+  jwt_payload = try(local.jwt_parts[1], "")
+  payload_padding = local.jwt_payload == "" ? "" : (
+    length(local.jwt_payload) % 4 == 0 ? "" :
+    length(local.jwt_payload) % 4 == 2 ? "==" :
+    length(local.jwt_payload) % 4 == 3 ? "=" :
+    ""
+  )
+
+  jwt_username = try(
+    regex(
+      "/users/([^/]+)",
+      jsondecode(base64decode("${local.jwt_payload}${local.payload_padding}"))["sub"]
+    )[0],
+    ""
+  )
+
+  username = coalesce(
+    local.jwt_username != "" ? local.jwt_username : null,
+    var.username_field == "email" ? data.coder_workspace_owner.me.email : data.coder_workspace_owner.me.name
+  )
   jfrog_host = split("://", var.jfrog_url)[1]
   common_values = {
     JFROG_URL                = var.jfrog_url