fix: invitation accept-link rendering as null in invite/resend/update emails

[samark231]

Summary of Changes

Fixes the "Accept Invitation" button in team/role invitation emails resolving to a broken null link (DNS NXDOMAIN). When a user is invited to a team with a role (e.g. COUNSELLOR), the email's login URL was computed incorrectly and rendered as the literal string null.

Root cause: in InviteUserService.sendInvitationEmail, the null-guard checked learnerPortalUrl but assigned adminPortalUrl. For institutes that have a learner portal URL set but a null admin portal URL (the common case — admin_portal_base_url is a nullable column and Hibernate bypasses its DB default), the guard passed and overwrote the safe default with null. That null was then formatted into the email's href.

A second, independent bug is also fixed: the resend/update invitation emails used a static @Value field (ADMIN_LOGIN_URL), which Spring cannot inject — so it was always null, producing a permanent null/login link for every resend/update.

Backend:

• InviteUserService.sendInvitationEmail: guard now checks adminPortalUrl (the field actually used) via StringUtils.hasText; falls back to https://dash.vacademy.io when unset.
• Added normalizeUrl helper that prepends https:// to schemeless portal URLs (DB column default and some stored values have no scheme), preventing relative/broken links.
• InviteUserService.sendReminderEmail: now resolves the institute's admin portal URL (same logic + fallback) and passes it into the reminder template.
• InviteUserEmailBody: removed the broken static @Value adminPortalClientUrl and ADMIN_LOGIN_URL constant; createReminderEmail now accepts an adminLoginUrl parameter.

Frontend:

• None.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

How Has This Been Tested?

• Invited a user to a team with the COUNSELLOR role against a local auth_service; confirmed the "Accept Invitation" email link now renders a valid URL (https://dash.vacademy.io for an institute with no admin portal URL) instead of null.
• Verified institutes with an explicit admin portal URL get that branded URL, scheme-normalized.
• Verified resend/update invitation emails now produce a valid login link instead of null/login.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes
• I have updated the documentation accordingly

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 26 complexity

Metric	Results
Complexity	26

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