fix: intro preauth client once

[pike1212]

Related issue

#712

Proposed changes

Only initializes oauth client once during config stage per config and doesn't initialize when creating new introspector.

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• I have read the contributing guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security. vulnerability, I
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[aeneasr]

Awesome! This looks much better :) These a few more things left to do but it's now something we can release :))

[aeneasr]

Awesome! I think we can use require/assert for the equals comparison but otherwise this is exactly what I imagined! thank you :)

[pike1212]

@aeneasr can this be merged?

[aeneasr]

Yes! :)

[aeneasr]

Thank you! :)