This commit serves two main purposes. First, it merges the code
for the two authentication providers, azure and oauth. To do this,
we no longer rely on the azure-specific MSAL library, but use a more
general library that we already use for non-azure providers.
Second, we change our authentication scheme from a
bearer token provided in the header and stored in a frontend service
to secure cookies. This eliminates an XSS attack vector as
the tokens are no longer accessible on the client side.

Previously, we used a dedicated local storage service, with the only
difference being that the get function returned an empty string
instead of null if the key did not exist. Therefore, this commit
removes the local storage service and uses the localstorage
directly, with some explicit null checks.

This documents how to use Keycloak as an identity provider
for the capella Collaboration Manager (CCM). This includes how to
properly configure a CCM client in Keycloak and how to set up
the configuration in CCM to use that client. However, it is important
to note that the documentation does not cover how to properly
configure and securely use Keycloak.

This commit primarily adds two columns to the user table,
the idp identifier and the email. The idp identifier is used to map
the idp user to the local user. Therefore, it is critical that the idp
claim used for this is unique per user. The following breaking changes
are introduced to the values.yaml file: The `jwt.usernameClaim' is
now moved to `claimMapping.username' and specifies the identity token
claim used for the username column. The `claimMapping.idpIdentifier'
is added, which specifies the identity token claim used for the
new idp identifier column and must be unique within the idp.
The `claimMapping.email` is added, which specifies the identity token
claim used for the new email column. The breaking changes are
detailed in the PR description and in the release notes.