client: add login capability

[anwyss]

GOAL Registered users can login

ACCEPTANCE CRITERIA

• [x] a login component is shown to every user at /login
• [x] with valid credentials, the user gets redirected to the profile page
• [x] with invalid credentials, the user stays on the login page
• [ ] the login button is disabled before request resolves

TECHNICAL NOTES

• [x] add the query login to the file graphql/authentication
• [x] rename authenticationEpic to signupEpic and rename file
• [x] add new epic in redux/epics/login for login parallel to signupEpic. It should send the query logIn with variables email and password and map response to the action LOG_IN_SUCCESS or LOG_IN_FAILURE
• [x] add action creator login in file redux/action-creators that creates an action that has the type LOG_IN and the payload email and password.
• [x] redirect to profile page on action LOG_IN_SUCCESS
• [x] stay on login page on action LOG_IN_FAILURE
• [x] update reducer authentication with case LOG_IN, LOG_IN_SUCCESS and LOG_IN_FAILURE

[axel-ob]

Hey Anna

thanks for going in much more detail on this! Does it make sense to keep two different boards though? I'm sure we track all issues (technical and overall) in https://github.com/orgs/re-CoV-er/projects/1? If you want more columns (review etc.), we can add them.

[anwyss]

for us it fits well to have a board with the technical slices. meaning, we take your issues and split them into these technical slices without all the business noise. This slice I added is lets say a "sub-slice" of your USM: Authentication - Signup & Login #11

[axel-ob]

OK for now. I'll create links between the respective issues(/PRs).