cellidresolver: cache lookup results in memory

it can take literally 5s or more on moby to synthesize cell results. caching will hopefully help that.

ols/resolver/cellid/cellidresolver.py

@@ -2,6 +2,7 @@ import logging
 import os.path
 import sqlite3
 from datetime import datetime
+from functools import lru_cache
 from typing import Optional
 
 from ..base import ResolverBase
@@ -36,6 +37,7 @@ class CellIdResolver(ResolverBase):
         cur = self.con.cursor()
         return cur.execute('PRAGMA user_version').fetchone()[0]
 
+    @lru_cache
     def search_network(self, radiotype, mcc, net, area, cell) -> Optional[dict]:
         cur = self.con.cursor()
         # radiotype is not required in observations
@@ -56,6 +58,7 @@ class CellIdResolver(ResolverBase):
         else:
             return None
 
+    @lru_cache
     def search_nearby(self, radiotype, mcc, net, area, cell) -> Optional[dict]:
         """
         synthesize a cell tower from towers whose `cell` id is close to the id of interest,