Add Swagger UI on /swagger

This includes a Swagger UI with an OpenAPI 3.0 JSON schema for easy
interactive demonstration and testing of the API. The JSON schema
was created with the standalone swagger-editor. Includes tests to
make sure that the /swagger and /docs/openapi.json paths are acce-
ssible.

dspace_statistics_api/app.py

@@ -1,5 +1,6 @@
 import falcon
 import psycopg2.extras
+from falcon_swagger_ui import register_swaggerui_app
 
 from .database import DatabaseManager
 from .stats import get_downloads, get_views
@@ -14,6 +15,14 @@ class RootResource:
             resp.body = f.read()
 
 
+class OpenAPIJSONResource:
+    def on_get(self, req, resp):
+        resp.status = falcon.HTTP_200
+        resp.content_type = "text/html"
+        with open("dspace_statistics_api/docs/openapi.json", "r") as f:
+            resp.body = f.read()
+
+
 class AllStatisticsResource:
     @falcon.before(set_statistics_scope)
     def on_get(self, req, resp):
@@ -178,4 +187,18 @@ api.add_route("/community/{id_:uuid}", SingleStatisticsResource())
 api.add_route("/collections", AllStatisticsResource())
 api.add_route("/collection/{id_:uuid}", SingleStatisticsResource())
 
+# Swagger configuration
+SWAGGERUI_URL = "/swagger"  # without trailing slash
+SCHEMA_URL = "/docs/openapi.json"
+api.add_route("/docs/openapi.json", OpenAPIJSONResource())
+
+register_swaggerui_app(
+    api,
+    SWAGGERUI_URL,
+    SCHEMA_URL,
+    config={
+        "supportedSubmitMethods": ["get", "post"],
+    },
+)
+
 # vim: set sw=4 ts=4 expandtab: