Generator-jhipster: Update Keycloak to 7.0.0

[DanielFran]

Overview of the feature request

Update Keycloak to latest version: see https://www.keycloak.org/docs/latest/release_notes/index.html#keycloak-7-0-0

Refer to https://www.keycloak.org/docs/7.0/upgrading/index.html#migrating-to-7-0-0

Need changes on:

• https://github.com/jhipster/generator-jhipster/blob/master/generators/generator-constants.js#L32
• https://github.com/jhipster/generator-jhipster/blob/master/generators/docker-compose/templates/realm-config/jhipster-realm.json.ejs
• https://github.com/jhipster/generator-jhipster/blob/master/generators/server/templates/src/main/docker/config/realm-config/jhipster-realm.json.ejs

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[SudharakaP]

@DanielFran : Would you be okay with me to submitting a pull request for this? 😄

[DanielFran]

@SudharakaP Too late, I already submitted one.
But you still can review the PR...

[SudharakaP]

@DanielFran : No worries; that's fine. Just thought I could get it off your hands as it's a quick fix. 😄