docs: Update certificate information in readme

Author: Technoguyfication

README.md

@@ -104,7 +104,7 @@ Complete source code is available in [BasicWrite example](examples/BasicWrite/Ba
 ## Connecting to InfluxDB Cloud 2
 Instead of setting up a local InfluxDB 2 server, it is possible to quickly [start with InfluxDB Cloud 2](https://docs.influxdata.com/influxdb/cloud/get-started/) with a [Free Plan](https://docs.influxdata.com/influxdb/cloud/account-management/pricing-plans/#free-plan).
 
-InfluxDB Cloud uses secure communication over TLS (https). We need to tell the client to trust this connection. The paragraph bellow describes how to set trusted connection. However, InfluxDB cloud servers have only 3 months validity period. Their CA certificate, included in this library, has the validity period a year. This is not much for a long running device. To avoid such limitation you can use an untrusted connection. Check [Skipping certification validation](#skipping-certificate-validation) for more details. 
+InfluxDB Cloud uses secure communication over TLS (https). We need to tell the client to trust this connection. The paragraph bellow describes how to set trusted connection. However, InfluxDB cloud servers have only 3 months validity period. Their CA certificate, included in this library, is valid until 2035. Check [Skipping certification validation](#skipping-certificate-validation) for more details. 
 
 Connecting an Arduino client to InfluxDB Cloud server requires a few additional steps comparing to connecting to local server.
 
@@ -316,44 +316,40 @@ You can use a custom server certificate by exporting it, e.g. using a web browse
 // Server certificate in PEM format, placed in the program (flash) memory to save RAM
 const char ServerCert[] PROGMEM =  R"EOF(
 -----BEGIN CERTIFICATE-----
-MIIGEzCCA/ugAwIBAgIQfVtRJrR2uhHbdBYLvFMNpzANBgkqhkiG9w0BAQwFADCB
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 -----END CERTIFICATE-----
 )EOF";
 
 // Alternatively, use a fingerprint of server certificate to set trust. Works only for ESP8266.
-const char ServerCert[] PROGMEM = "9B:62:0A:63:8B:B1:D2:CA:5E:DF:42:6E:A3:EE:1F:19:36:48:71:1F";
+const char ServerCert[] PROGMEM = "cabd2a79a1076a31f21d253635cb039d4329a5e8";
 ```
 
 ### InfluxDb 2
@@ -390,9 +386,11 @@ Another important prerequisite to successfully validate a server or CA certifica
 :information_source: Time synchronization is not required for validating server certificate via SHA1 fingerprint.
 
 ### Skipping certificate validation
-Server certificates have limited validity period, often only a few months. It will be necessary to frequently change trusted certificate in the source code and reflashing the device. A solution could be using OTA update, but you will still need to care about certificate validity and updating it ahead of time to avoid connection failures.
+The CA certificate provided with the library is ISRG Root X1. This certificate lasts a very long time, until 2035. It is not necessary to update your device until then when using ISRG Root X1.
 
-Most comfortable way is to skip server certificate validation completely by establishing untrusted connection. This is done with the help of `InfluxDBClient::setInsecure()` method. 
+If you are using your own certificate, plase keep in mind server certificates have limited validity period, often only a few months. It will be necessary to frequently change trusted certificate in the source code and reflashing the device. A solution could be using OTA update, but you will still need to care about certificate validity and updating it ahead of time to avoid connection failures.
+
+The best way to prevent frequent updates is to use a root certificate like the one provided with the library. If you are unable to use a root certificate from a trusted authority, you may want to use insecure mode instead. This is done with the help of `InfluxDBClient::setInsecure()` method. 
 You will also save space in flash (and RAM) by leaving certificate param empty when calling constructor or `setConnectionParams` method.
 
 :memo: The `InfluxDBClient::setInsecure()` method must be called before calling any function that will establish connection. The best place to call it is in the `setup` method: