Ability to mask keys in the logs

2019/03/05 15:00:37 [info] 25#25: *3 [lua] proxy.lua:81: output_debug_headers(): usage: usage%5Bhello%5D=1&usage%5Ball%5D=1 credentials: user_key={color:#DE350B}{color:#DE350B}123456789{color}, client: 172.17.0.1, server: _, request: "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1", host: "localhost:8081"
2019/03/05 15:00:37 [info] 25#25: *3 [lua] proxy.lua:148: apicast cache miss key: 2555417761735:{color:#DE350B}123456789{color}:usage%5Bhello%5D=1&usage%5Ball%5D=1 value: nil, client: 172.17.0.1, server: _, request: "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1", host: "localhost:8081"
2019/03/05 15:00:37 [info] 25#25: *3 [lua] balancer.lua:108: set_current_peer(): balancer set peer 54.83.62.186:443 ok: true err: nil while connecting to upstream, client: 172.17.0.1, server: _, request: "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1", subrequest: "/transactions/authrep.xml", host: "localhost:8081"
2019/03/05 15:00:38 [info] 25#25: *3 [lua] backend_client.lua:139: call_backend_transaction(): backend client uri: https://su1.3scale.net/transactions/authrep.xml?service_token=abcde&service_id=2555417761735&usage%5Bhello%5D=1&usage%5Ball%5D=1&user_key={color:#DE350B}123456789{color} ok: true status: 200 body:  error: nil while sending to client, client: 172.17.0.1, server: _, request: "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1", host: "localhost:8081"
2019/03/05 15:00:38 [info] 25#25: *3 [lua] cache_handler.lua:43: cache_handler(): apicast cache write key: 2555417761735:{color:#DE350B}123456789{color}:usage%5Bhello%5D=1&usage%5Ball%5D=1, ttl: nil while sending to client, client: 172.17.0.1, server: _, request: "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1", host: "localhost:8081"
2019/03/05 15:00:38 [info] 25#25: *3 [lua] balancer.lua:108: set_current_peer(): balancer set peer 18.214.132.12:443 ok: true err: nil while connecting to upstream, client: 172.17.0.1, server: _, request: "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1", host: "echo-api.3scale.net"
2019/03/05 15:00:38 [info] 25#25: *3 [lua] proxy.lua:331: [async] skipping after action, no cached key while sending to client, client: 172.17.0.1, server: _, request: "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1", upstream: "https://18.214.132.12:443/hello?user_key={color:#DE350B}123456789{color}", host: "echo-api.3scale.net"
[05/Mar/2019:15:00:38 +0000] localhost:8080 172.17.0.1:35684 "GET /hello?user_key={color:#DE350B}123456789{color} HTTP/1.1" 200 718 (12.444) 0
2019/03/05 15:00:38 [info] 25#25: *3 client 172.17.0.1 closed keepalive connection