[Coral-Schema] Disambiguate nested record namespaces with numeric suffixes

[ruolin59]

What changes are proposed in this pull request, and why are they necessary?

• Fix Avro namespace collisions when a parent schema contains multiple fields that reference nested records with the same name but different original namespaces, by doing the following
  • Detect collisions per parent record (same record name, different original namespaces).
  • Assign stable numeric suffixes to the reconstructed namespace of colliding records (e.g., “-0”, “-1”, …), keeping non-colliding cases unchanged.

This approach:

• Prevents fully-qualified name collisions.
• Avoids leaking source/original namespaces into generated schemas.
• Minimizes changes: only colliding records get suffixes; everything else remains the same.

Simple example:
Input (two fields with the same record name):

{
  "type": "record",
  "name": "Parent",
  "namespace": "com.app",
  "fields": [
    { "name": "ctxA", "type": ["null", {"type":"record","name":"Ctx","namespace":"com.foo"}] },
    { "name": "ctxB", "type": ["null", {"type":"record","name":"Ctx","namespace":"com.bar"}] }
  ]
}

• Before (with collision): both nested records reconstructed to the same namespace (e.g., "com.app.Parent"), and has the same name (eg. "Ctx"), which is invalid.
• After (no collision):
  • ctxA non-null type namespace: "com.app.Parent-0", with name "Ctx"
  • ctxB non-null type namespace: "com.app.Parent-1", with name "Ctx"

How was this patch tested?

• Added unit tests in SchemaUtilitiesTests:
• Verifies collision handling for nullable union fields with same record name.
• Verifies collision handling for direct nested record fields (non-union) with same record name.
• Asserts distinct namespaces with numeric suffixes (e.g., endsWith("-0") / endsWith("-1")).
• Ran full module tests; all existing tests pass without updating expected .avsc files.
• Verified manually in Spark-shell that the namespace collision was fixed for the offending table

[aastha25]

Thanks for the PR, purely based on the PR description, should the namespace unique-fication be at the conflicting layer?

"com.app.Parent.Ctx0"
"com.app.Parent.Ctx1"

Also, some of the testing done section has company specific internal details, that can be skipped in this public forum.

[ruolin59]

@aastha25

Thanks for the PR, purely based on the PR description, should the namespace unique-fication be at the conflicting layer?

"com.app.Parent.Ctx0"
"com.app.Parent.Ctx1"

This was a mistake in the description. Ctx is not part of the namespace, as it is the actual name where the collision occurs. I've updated the description to fix