[JIRA] added jira oauth2 integration to examples (#910)

* added jira oauth2 example

* fixed flake8 issues

Author: sureshdsk

examples/jira/jira_oauth2.py

@@ -0,0 +1,85 @@
+# Example server with Flask demonstrating use of Jira OAuth 2.0.
+# Server needs to be deployed. Example code is requesting access token from
+# Jira. User has to grant access rights. After authorization the
+# token and Using access token, Jira cloud ID is identified and
+# the available projects are returned.
+
+from requests_oauthlib import OAuth2Session
+from atlassian.jira import Jira
+from flask import Flask, request, redirect, session
+import requests
+
+app = Flask(__name__)
+app.secret_key = ""
+
+# JIRA OAuth URLs
+authorization_base_url = "https://auth.atlassian.com/authorize"
+token_url = "https://auth.atlassian.com/oauth/token"
+
+
+# Create OAuth 2.0 Integration in Atlassian developer console
+# https://developer.atlassian.com/console/myapps/
+# Click Authorization →  “Configure” under OAuth 2.0 and
+# Enter callback url  {server}/callback and save
+# Click “Permissions” and Add “Jira platform REST API” and other required permissions.
+# Click “Configure” under Jira platform REST API and Add permissions like
+# “View user profiles“, “View Jira issue data“ and  “Create and manage issues”
+# Goto setting and copy client id and secret.
+
+client_id = ""
+client_secret = ""
+redirect_uri = ""  # {server_url}/callback
+
+
+# 2. Redirect to Jira for authorization
+# The server request to {server_url}/login is redirected to Jira.
+# The user is asked to grant access permissions.
+@app.route("/login")
+def login():
+    scope = ["read:me", "read:jira-user", "read:jira-work"]
+    audience = "api.atlassian.com"
+
+    jira_oauth = OAuth2Session(client_id, scope=scope, redirect_uri=redirect_uri)
+    authorization_url, state = jira_oauth.authorization_url(
+        authorization_base_url,
+        audience=audience,
+    )
+    session["oauth_state"] = state
+    return redirect(authorization_url)
+
+
+# 3. Jira redirects user to callback url with authorization code
+# This should be set to {server_url}/callback.
+# Access token is fetched using authorization code
+@app.route("/callback")
+def callback():
+    jira_oauth = OAuth2Session(client_id, state=session["oauth_state"], redirect_uri=redirect_uri)
+    token_json = jira_oauth.fetch_token(token_url, client_secret=client_secret, authorization_response=request.url)
+    return "Token: {}<p />Projects: {}".format(token_json, ", ".join(get_projects(token_json)))
+
+
+# 4. Access Token used for Jira Python API
+# Using access token, accessible resources are fetched and
+# First resource id is taken as jira cloud id,
+# Jira Client library is called with  jira cloud id and token information.
+def get_projects(token_json):
+    req = requests.get(
+        "https://api.atlassian.com/oauth/token/accessible-resources",
+        headers={
+            "Authorization": "Bearer {}".format(token_json["access_token"]),
+            "Accept": "application/json",
+        },
+    )
+    req.raise_for_status()
+    resources = req.json()
+    cloud_id = resources[0]["id"]
+
+    oauth2_dict = {
+        "client_id": client_id,
+        "token": {
+            "access_token": token_json["access_token"],
+            "token_type": "Bearer",
+        },
+    }
+    jira = Jira(url="https://api.atlassian.com/ex/jira/{}".format(cloud_id), oauth2=oauth2_dict)
+    return [project["name"] for project in jira.projects()]