docfix resource doc for Get user by PROVIDER AND USERNAME

Author: simonredfern

obp-api/src/main/scala/code/api/v5_1_0/APIMethods510.scala

@@ -2468,10 +2468,26 @@ trait APIMethods510 {
       "/users/provider/PROVIDER/username/USERNAME",
       "Get User by USERNAME",
       s"""Get user by PROVIDER and USERNAME
+         |
+         |Get a User by their authentication provider and username.
+         |
+         |**URL Parameters:**
+         |
+         |* PROVIDER - The authentication provider (e.g., http://127.0.0.1:8080, google.com, OBP)
+         |* USERNAME - The username at that provider (e.g., obpstripe, john.doe)
+         |
+         |**Important:** The PROVIDER parameter can contain special characters like slashes and colons.
+         |For example, if the provider is "http://127.0.0.1:8080", the full URL would be:
+         |
+         |`GET /obp/v5.1.0/users/provider/http://127.0.0.1:8080/username/obpstripe`
+         |
+         |The API will correctly parse the provider value even with these special characters.
+         |
+         |**To find valid providers**, use the GET /providers endpoint.
          |
          |${userAuthenticationMessage(true)}
          |
-         |CanGetAnyUser entitlement is required,
+         |CanGetAnyUser entitlement is required.
          |
       """.stripMargin,
       EmptyBody,