Your documentation have only java integration example and is using a Google api. If you, could provide some proper doc or and reference so that I can use the follow in other language too.
Doc like, what will be the payload for which post request.
Example - Making a POST request on https://{project}.atlassian.net/plugins/servlet/oauth/request-token expect payload like
oauth_signature_method:RSA-SHA1
oauth_timestamp:1516339431
oauth_nonce:20171113121052483
oauth_signature:MIGfMA0GCSqGSIb3DQEBAQUAA4GNAsdfasdfsdDCBiQKBgQC3y9sc3nhe73xBHELMrd+hXew9↵zu8KXqs1wTlTfasda0LYNZ96hUIFRKz0R+wPbmo38Y/rghvywmasdEYl4TQfVqGuY7kyxi↵DJkz4JrGKYHnLEpuYGjZAaasdauWknU4Wsdl4A9ssuXgZ3YjoUYQasd94v0qcf1m0R9w/4F8C↵0hDqgoTBbcguvJ/8fQIDAQAB
oauth_callback:http://example.com
and Rather than that I am getting this 
Error - net.oauth.OAuthException: java.security.SignatureException: Signature length not correct: got 632 but was expecting 128
here is the image -
P.S. - I am working in .net core 2.0 and want to use OAuth flow