Ensure we populate sane defaults for NULL values (#583)

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## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following PR tries to ensure sane defaults for entries that for one
reason or another have NULL values for some of their properties.

## How Has This Been Tested?
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tested? -->

## Breaking Changes
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## Types of changes
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the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
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that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
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---------

Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>

internal/database/migrations/008_separate_official_metadata.sql

@@ -6,7 +6,7 @@ BEGIN;
 -- Add new columns for official metadata and core identifiers
 ALTER TABLE servers ADD COLUMN server_name VARCHAR(255);
 ALTER TABLE servers ADD COLUMN version VARCHAR(255);
-ALTER TABLE servers ADD COLUMN status VARCHAR(50);
+ALTER TABLE servers ADD COLUMN status VARCHAR(50) DEFAULT 'active';
 ALTER TABLE servers ADD COLUMN published_at TIMESTAMP WITH TIME ZONE;
 ALTER TABLE servers ADD COLUMN updated_at TIMESTAMP WITH TIME ZONE;
 ALTER TABLE servers ADD COLUMN is_latest BOOLEAN;
@@ -38,16 +38,16 @@ BEGIN
             -- Note: status is at top level in old format, not in official_meta
             UPDATE servers
             SET
-                status = COALESCE(NULLIF(rec.value->>'status', 'null'), 'active'),
-                published_at = (official_meta->>'publishedAt')::TIMESTAMP WITH TIME ZONE,
-                updated_at = (official_meta->>'updatedAt')::TIMESTAMP WITH TIME ZONE,
-                is_latest = (official_meta->>'isLatest')::BOOLEAN
+                status = rec.value->>'status',
+                published_at = COALESCE((official_meta->>'publishedAt')::TIMESTAMP WITH TIME ZONE, NOW()),
+                updated_at = COALESCE((official_meta->>'updatedAt')::TIMESTAMP WITH TIME ZONE, NOW()),
+                is_latest = COALESCE((official_meta->>'isLatest')::BOOLEAN, true)
             WHERE version_id = rec.version_id;
         ELSE
             -- Handle records without official metadata (set defaults)
             UPDATE servers
             SET
-                status = COALESCE(NULLIF(rec.value->>'status', 'null'), 'active'),
+                status = rec.value->>'status',
                 published_at = NOW(),
                 updated_at = NOW(),
                 is_latest = true
@@ -82,11 +82,53 @@ SELECT migrate_official_metadata();
 -- Drop the migration function
 DROP FUNCTION migrate_official_metadata();
 
+-- Safety check: Normalize invalid status values before adding NOT NULL constraints
+-- This handles: NULL (missing field), empty string, string "null", and any invalid values
+UPDATE servers
+SET status = 'active'
+WHERE status IS NULL
+   OR status = ''
+   OR status = 'null'
+   OR status NOT IN ('active', 'deprecated', 'deleted');
+
+UPDATE servers SET published_at = NOW() WHERE published_at IS NULL;
+
+-- Safety check: Ensure updated_at is never NULL
+UPDATE servers SET updated_at = NOW() WHERE updated_at IS NULL;
+
+-- For is_latest: preserve existing true values, handle NULLs deterministically
+-- First, for servers where NO version has is_latest=true, mark the most recent as latest
+WITH servers_without_latest AS (
+    SELECT DISTINCT s1.server_name
+    FROM servers s1
+    WHERE NOT EXISTS (
+        SELECT 1 FROM servers s2
+        WHERE s2.server_name = s1.server_name
+        AND s2.is_latest = true
+    )
+),
+latest_versions AS (
+    SELECT s.server_name, MAX(s.published_at) as max_published
+    FROM servers s
+    INNER JOIN servers_without_latest swl ON s.server_name = swl.server_name
+    GROUP BY s.server_name
+)
+UPDATE servers s
+SET is_latest = true
+FROM latest_versions lv
+WHERE s.server_name = lv.server_name
+  AND s.published_at = lv.max_published
+  AND s.is_latest IS NULL;
+
+-- Finally, set remaining NULLs to false
+UPDATE servers SET is_latest = false WHERE is_latest IS NULL;
+
 -- Make the new columns NOT NULL now that all records have values
 ALTER TABLE servers ALTER COLUMN server_name SET NOT NULL;
 ALTER TABLE servers ALTER COLUMN version SET NOT NULL;
 ALTER TABLE servers ALTER COLUMN status SET NOT NULL;
 ALTER TABLE servers ALTER COLUMN published_at SET NOT NULL;
+ALTER TABLE servers ALTER COLUMN updated_at SET NOT NULL;
 ALTER TABLE servers ALTER COLUMN is_latest SET NOT NULL;
 
 -- Drop the old primary key constraint
@@ -112,7 +154,7 @@ CREATE INDEX idx_servers_name_version ON servers (server_name, version);
 CREATE INDEX idx_servers_name_latest ON servers (server_name, is_latest) WHERE is_latest = true;
 CREATE INDEX idx_servers_status ON servers (status);
 CREATE INDEX idx_servers_published_at ON servers (published_at DESC);
-CREATE INDEX idx_servers_updated_at ON servers (updated_at DESC) WHERE updated_at IS NOT NULL;
+CREATE INDEX idx_servers_updated_at ON servers (updated_at DESC);
 
 -- Ensure only one version per server can be marked as latest
 CREATE UNIQUE INDEX idx_unique_latest_per_server