Support multiple oauth flows

**Description**
It would be nice if we could support multiple oauth2 flows in swaggerui/openapi. Currently only one flow can be enabled.

We could expand the configuration and use the name of the flow as key. This could also simplify the part in the OpenApiFactory and could be a nice addition.

Ref: https://swagger.io/docs/specification/authentication/oauth2/

**Example**
```
oauth:
enabled: true
flows:
implicit:
clientId: foo
clientSecret: bar
authorizationUrl: 'oauth2.local'
scopes: []
client_credentials:
clientId: foo
clientSecret: bar
tokenUrl: 'oauth2.local'
scopes: []
```