SimpleChatTC:SimpleProxy: Validate deps wrt enabled service paths

helps ensure only service paths that can be serviced are enabled

Use same to check for pypdf wrt pdftext

tools/server/public_simplechat/local.tools/simpleproxy.py

@@ -48,7 +48,11 @@ gConfigType = {
 
 gConfigNeeded = [ '--allowed.schemes', '--allowed.domains', '--bearer.insecure' ]
 
-gAllowedCalls = [ "urltext", "urlraw", "pdftext" ]
+gAllowedCalls = {
+    "urltext": [],
+    "urlraw": [],
+    "pdftext": [ "pypdf" ]
+    }
 
 
 def bearer_transform():
@@ -157,6 +161,7 @@ def handle_aum(ph: ProxyHandler, pr: urllib.parse.ParseResult):
     Handle requests to aum path, which is used in a simple way to
     verify that one is communicating with this proxy server
     """
+    import importlib
     queryParams = urllib.parse.parse_qs(pr.query)
     url = queryParams['url']
     print(f"DBUG:HandleAUM:Url:{url}")
@@ -165,8 +170,14 @@ def handle_aum(ph: ProxyHandler, pr: urllib.parse.ParseResult):
         ph.send_error(400, f"WARN:HandleAUM:MissingUrl/UnknownQuery?!")
         return
     urlParts = url.split('.',1)
-    if not (urlParts[0] in gAllowedCalls):
-        ph.send_error(403, f"WARN:HandleAUM:Forbidded:{urlParts[0]}")
+    if gAllowedCalls.get(urlParts[0], None) == None:
+        ph.send_error(403, f"WARN:HandleAUM:Forbidden:{urlParts[0]}")
+        return
+    for dep in gAllowedCalls[urlParts[0]]:
+        try:
+            importlib.import_module(dep)
+        except ImportError as exc:
+            ph.send_error(400, f"WARN:HandleAUM:{urlParts[0]}:Support module [{dep}] missing or has issues")
             return
     print(f"INFO:HandleAUM:Availability ok for:{urlParts[0]}")
     ph.send_response_only(200, "bharatavarshe")