Add yieldgen report endpoint to API

Fixes #1122. An RPC client can request the list
of coinjoins as shown in the file datadir/logs/yigen-statement.csv.
Authentication is not required, nor a specific wallet, as this is
a global list of all coinjoins done so far. A 404 is returned if
the file has not yet been created (no maker operations).

docs/api/wallet-rpc.yaml

@@ -123,6 +123,16 @@ paths:
           $ref: "#/components/responses/ListWallets-200-OK"
         '404':
           $ref: '#/components/responses/404-NotFound'
+  /wallet/yieldgen/report:
+    get:
+      summary: get latest report on yield generating activity
+      operationId: yieldgenreport
+      description: get list of coinjoins taken part in as maker (across all wallets)
+      responses:
+        '200':
+          $ref: "#/components/responses/YieldGenReport-200-OK"
+        '404':
+          $ref: '#/components/responses/404-NotFound'
   /wallet/{walletname}/address/new/{mixdepth}:
     get:
       security:

jmclient/jmclient/wallet_rpc.py

@@ -88,6 +88,11 @@ class TransactionFailed(Exception):
 class NotEnoughCoinsForMaker(Exception):
     pass
 
+# raised when we cannot read data from our
+# yigen-statement csv file:
+class YieldGeneratorDataUnreadable(Exception):
+    pass
+
 def get_ssl_context(cert_directory):
     """Construct an SSL context factory from the user's privatekey/cert.
     TODO:
@@ -299,6 +304,11 @@ class JMWalletDaemon(Service):
         request.setResponseCode(409)
         return self.err(request, "Maker could not start, no coins.")
 
+    @app.handle_errors(YieldGeneratorDataUnreadable)
+    def yieldgenerator_report_unavailable(self, request, failure):
+        request.setResponseCode(404)
+        return self.err(request, "Yield generator report not available.")
+
     def check_cookie(self, request):
         #part after bearer is what we need
         try:
@@ -600,6 +610,29 @@ class JMWalletDaemon(Service):
             self.services["maker"].stopService()
             return make_jmwalletd_response(request, status=202)
 
+        def get_json_yigen_report(self):
+            try:
+                datadir = os.path.join(jm_single().config.datadir, "logs")
+                with open(os.path.join(datadir, "yigen-statement.csv"), "rb") as f:
+                    yigen_data_raw = f.readlines()
+                return json.loads(yigen_data_raw)
+            except:
+                raise YieldGeneratorDataUnreadable()
+
+        @app.route('/wallet/yieldgen/report', methods=['GET'])
+        def yieldgen_report(self, request):
+            # Note that this is *not* a maker function, and
+            # not wallet specific (the report aggregates over time,
+            # even with different wallets), and does not require
+            # an authenticated session (it reads the filesystem, like
+            # /all)
+            # note: can raise, most particularly if file has not been
+            # created because maker never ran (or deleted):
+            yigen_data = self.get_json_yigen_report()
+            # this is the successful case; note the object can
+            # be an empty list:
+            return make_jmwalletd_response(request, yigen_data=yigen_data)
+
         @app.route('/wallet/<string:walletname>/lock', methods=['GET'])
         def lockwallet(self, request, walletname):
             print_req(request)