changed the hashing algorithm from sha1 to sha256 due to security problems

[lucianidev]

hello,
in the issue #989 the user references a vulnerability in the hashing algorithm sha1. The hashing method resulted vulnerable to hash collision, making it insecure. I changed the hashing method from sha1 to sha256 making it more secure. Tell me about any problems.
I hope you have a good day

Documentation:
https://crypto.stackexchange.com/questions/48289/how-secure-is-sha1-what-are-the-chances-of-a-real-exploit
https://www.quora.com/How-secure-is-SHA1-What-are-the-chances-of-a-real-exploit
https://stackoverflow.com/questions/38038841/why-is-sha-1-considered-insecure

[jonchurch]

sha1 is being used as a fast and efficient hash to detect changes in the session object

It is not cryptographically relevant, nor used for signing purposes.

[krko12345]

Hello team, is this going to be addressed at some point soon?
Session is being reported as vulnerability by monitoring tools because of its use of sha1.