consent: Fix concurrent write and read on map(#1721)

[rickwang7712]

Related issue

#1721
@aeneasr

Proposed changes

Fix fatal error: concurrent map iteration and map write by wrapping read part with lock.

Checklist

• [ x] I have read the contributing guidelines
• [ x] I have read the security policy
• [x ] I confirm that this pull request does not address a security vulnerability. If this pull request addresses a security
  vulnerability, I confirm that I got green light (please contact security@ory.sh) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works
• [ x] I have added necessary documentation within the code base (if appropriate)
• [x ] I have documented my changes in the developer guide (if appropriate)

Further comments

@aeneasr I was trying to add tests to catch problem like this, but I met other database's error. And I currently have no time for this... I'm sorry.
Do you think I can open another issue for adding test for it?

[aeneasr]

Thank you! :)