Fix kraken account-alias config mismatch

Rename `Client._name` -> `Client._key_descr` so the attr actually
describes what it holds (the `key_descr` field from `brokers.toml`). In
`open_trade_dialog()` look up the account-alias via `conf['accounts']`
and raise a `ConfigurationError` with a config-file example when no
matching entry exists.

Deats,
- `api.py`: rename `name` param/attr to `key_descr`, add docstring to
  `get_client()`, pull `conf['key_descr']` into a named local.
- `broker.py`: replace `acc_name` with `fqan` (fully-qualified account
  name), add accounts dict validation with actionable error msg.
- `brokers.toml`: add `src_fiat`, `accounts.spot` entry, and comments
  explaining the required field relationships.

(this commit-msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

config/brokers.toml

@@ -32,7 +32,14 @@ option.log.disabled = true
 
 
 [kraken]
-key_descr = ''
+# the reference fiat asset as can be set
+# in an account's web-trading-UI prefs.
+src_fiat = 'usd'
+
+# NOTE for account defs, the following
+# lines must match as follows.
+accounts.spot = 'spot'
+key_descr = 'spot'
 api_key = ''
 secret = ''
 # ------ kraken ------

piker/brokers/kraken/api.py

@@ -147,17 +147,14 @@ class Client:
         config: dict[str, str],
         httpx_client: httpx.AsyncClient,
 
-        name: str = '',
+        key_descr: str = '',
         api_key: str = '',
         secret: str = ''
     ) -> None:
-
         self._sesh: httpx.AsyncClient = httpx_client
-
-        self._name = name
+        self._key_descr = key_descr
         self._api_key = api_key
         self._secret = secret
-
         self.conf: dict[str, str] = config
 
     @property
@@ -681,7 +678,13 @@ class Client:
 
 @acm
 async def get_client() -> Client:
+    '''
+    Load and deliver a `.kraken.api.Client`.
 
+    When defined, inject any config delivered from the user's
+    `brokers.toml` config file.
+
+    '''
     conf: dict[str, Any] = get_config()
     async with httpx.AsyncClient(
         base_url=_url,
@@ -692,13 +695,14 @@ async def get_client() -> Client:
         # connections=4
     ) as trio_client:
         if conf:
+            api_key_descr: str = conf['key_descr']
             client = Client(
                 conf,
                 httpx_client=trio_client,
 
                 # TODO: don't break these up and just do internal
                 # conf lookups instead..
-                name=conf['key_descr'],
+                key_descr=api_key_descr,
                 api_key=conf['api_key'],
                 secret=conf['secret']
             )

piker/brokers/kraken/broker.py

@@ -133,7 +133,6 @@ class BrokerClient:
 
 
 async def handle_order_requests(
-
     ws: NoBsWs,
     client: Client,
     ems_order_stream: tractor.MsgStream,
@@ -475,8 +474,20 @@ async def open_trade_dialog(
             )
 
         # auth required block
-        acctid = client._name
-        acc_name = 'kraken.' + acctid
+        conf: dict = client.conf
+        accounts: dict = conf.get('accounts')
+        acctid: str = client._key_descr
+        if not accounts.get(acctid):
+            raise ConfigurationError(
+                f'No API-key found for account-alias defined as {acctid!r} !\n'
+                f'\n'
+                f'Did set a `kraken.accounts.*` entry in your `brokers.toml`?\n'
+                f'It should look something like,\n'
+                f'\n'
+                f'[kraken]\n'
+                f'accounts.{acctid} = {acctid!r}\n'
+            )
+        fqan: str = f'kraken.{acctid}'
 
         # task local msg dialog tracking
         apiflows = OrderDialogs()
@@ -595,7 +606,10 @@ async def open_trade_dialog(
                 acctid,
             )
             # sync with EMS delivering pps and accounts
-            await ctx.started((ppmsgs, [acc_name]))
+            await ctx.started((
+                ppmsgs,
+                [fqan],
+            ))
 
             # TODO: ideally this blocks the this task
             # as little as possible. we need to either do
@@ -649,7 +663,7 @@ async def open_trade_dialog(
                     acnt=acnt,
                     ledger=ledger,
                     acctid=acctid,
-                    acc_name=acc_name,
+                    acc_name=fqan,
                     token=token,
                 )