whosgonna created an issue (kamailio/kamailio#4332)

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### Description

We received a INVITE with non-ascii characters in the authentication username. The character set and collation of the subscriber table is `latin1` and `latin1_swedish_ci`. This generated the following failure (DB connection names are `primary` and `secondary`):

``` 3(9) ERROR: db_mysql [km_dbase.c:127]: db_mysql_submit_query(): driver error on query: Illegal mix of collations (latin1_swedish_ci,IMPLICIT) and (utf8mb4_general_ci,COERCIBLE) for operation '=' (1267) 3(9) ERROR: <core> [lib/srdb1/db_query.c:158]: db_do_query_internal(): error while submitting query 3(9) WARNING: db_cluster [dbcl_api.c:513]: db_cluster_query(): serial operation - failure on cluster [db] (9/0) [primary] 3(9) ERROR: db_mysql [km_dbase.c:127]: db_mysql_submit_query(): driver error on query: Illegal mix of collations (latin1_swedish_ci,IMPLICIT) and (utf8mb4_general_ci,COERCIBLE) for operation '=' (1267) 3(9) ERROR: <core> [lib/srdb1/db_query.c:158]: db_do_query_internal(): error while submitting query 3(9) WARNING: db_cluster [dbcl_api.c:513]: db_cluster_query(): serial operation - failure on cluster [db] (8/0) [secondary] 3(9) ERROR: db_cluster [dbcl_api.c:513]: db_cluster_query(): no successful read on cluster [db] 3(9) ERROR: auth_db [authorize.c:180]: get_ha1(): failed to query database 3(9) ERROR: [DIGEST_AUTH 60e4abd540674d4aa8961d380411585e@0.0.0.0 INVITE-124524] Generic failure in authentication. Send '503 Server Error' and exit. ```

While using the limited character set in the database (and it's associated collation) is questionable, and I don't expect the query to succeed, the issue is that this single query failure is causing the connections to be disabled in the db_cluster.

### Troubleshooting

#### Reproduction

I haven't tried to reproduce this, but I would assume it's easy to do. I can probably mock it up in docker fairly quickly. As a safety measure, I'll be validating the field with `is_alphanum()`

#### Log Messages

(as in description)

#### SIP Traffic

The `Username` in the `Proxy-Authorization` header as "\uFEFF1011". As hex it's: ``` 22 ef bb bf 31 30 31 31 22 ```

### Possible Solutions

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### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 6.0.1 (aarch64/linux) flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, MEM_JOIN_FREE, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT-NOSMP, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_SEND_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: unknown compiled on 18:45:18 Mar 14 2025 with gcc 14.2.0

```

* **Operating System**:

<!-- Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...; Kernel details (output of `lsb_release -a` and `uname -a`) -->

Container: ``` NAME="Alpine Linux" ID=alpine VERSION_ID=3.21.2 PRETTY_NAME="Alpine Linux v3.21" HOME_URL="https://alpinelinux.org/" BUG_REPORT_URL="https://gitlab.alpinelinux.org/alpine/aports/-/issues" ```

Host: ``` NAME="Amazon Linux" VERSION="2023" ID="amzn" ID_LIKE="fedora" VERSION_ID="2023" PLATFORM_ID="platform:al2023" PRETTY_NAME="Amazon Linux 2023" ANSI_COLOR="0;33" CPE_NAME="cpe:2.3:o:amazon:amazon_linux:2023" HOME_URL="https://aws.amazon.com/linux/" BUG_REPORT_URL="https://github.com/amazonlinux/amazon-linux-2023" ```

Kernel (`uname -a)`: ``` Linux use2apocor01.n.fl.gg 6.1.56-82.125.amzn2023.aarch64 #1 SMP Tue Oct 10 17:03:29 UTC 2023 aarch64 aarch64 aarch64 GNU/Linux ```