Description of problem:
This seems to be regression of BZ 2139545.

During registration violation of unique constraint is hit as below

PG::UniqueViolation: ERROR: duplicate key value violates unique constraint "katello_available_module_streams_name_stream_context"

It seems like previous bugzilla just removed the log from /var/log/foreman/production, but postgresql still reflects same issue as below:

2023-07-18 13:31:36 CEST ERROR: duplicate key value violates unique constraint "katello_available_module_streams_name_stream_context"
2023-07-18 13:31:36 CEST DETAIL: Key (name, stream, context)=(python36, 3.6, 683b2e54) already exists.
2023-07-18 13:31:36 CEST STATEMENT: INSERT INTO "katello_available_module_streams" ("name", "stream", "context") VALUES ($1, $2, $3) RETURNING "id"
2023-07-18 13:31:36 CEST ERROR: duplicate key value violates unique constraint "katello_available_module_streams_name_stream_context"
2023-07-18 13:31:36 CEST DETAIL: Key (name, stream, context)=(ruby, 2.5, ad008a3a) already exists.
2023-07-18 13:31:36 CEST STATEMENT: INSERT INTO "katello_available_module_streams" ("name", "stream", "context") VALUES ($1, $2, $3) RETURNING "id"

Version-Release number of selected component (if applicable):
Satellite 6.13.2

How reproducible:
Always

Steps to Reproduce:
1. re-register RHEL8 host

Actual results:
/var/log/foreman/production.log
2023-07-18T13:31:36 [I|app|9ba09d93] Processing by Katello::Api::Rhsm::CandlepinDynflowProxyController#upload_profiles as JSON
2023-07-18T13:31:36 [I|app|9ba09d93] Parameters:

2023-07-18T13:31:36 [I|app|9ba09d93] Completed 200 OK in 167ms (Views: 6.1ms | ActiveRecord: 56.7ms | Allocations: 52327)

/var/lib/pgsql/data/log/postgresql-Tue.log
2023-07-18 13:31:36 CEST ERROR: duplicate key value violates unique constraint "katello_available_module_streams_name_stream_context"
2023-07-18 13:31:36 CEST DETAIL: Key (name, stream, context)=(python36, 3.6, 683b2e54) already exists.
2023-07-18 13:31:36 CEST STATEMENT: INSERT INTO "katello_available_module_streams" ("name", "stream", "context") VALUES ($1, $2, $3) RETURNING "id"
2023-07-18 13:31:36 CEST ERROR: duplicate key value violates unique constraint "katello_available_module_streams_name_stream_context"
2023-07-18 13:31:36 CEST DETAIL: Key (name, stream, context)=(ruby, 2.5, ad008a3a) already exists.
2023-07-18 13:31:36 CEST STATEMENT: INSERT INTO "katello_available_module_streams" ("name", "stream", "context") VALUES ($1, $2, $3) RETURNING "id"

Expected results:
No index violation.

Additional info:
Reported by customer but also reproduced locally, i will share reproducer details.