proxy.config.ssl.max_record_size rejects the documented value -1 (dynamic TLS record sizing)

[moonchen]

Summary

The documentation for proxy.config.ssl.max_record_size states that a value of -1
enables dynamic TLS record sizing. In practice the setting cannot be given that value:
configuration validation only accepts 0–16383, so -1 is rejected at startup and
the feature cannot be enabled through records.yaml.

Steps to reproduce

1. In records.yaml, set:

   records:
     ssl:
       max_record_size: -1

2. Start Traffic Server and check traffic.out.

Expected behavior

Per the documentation, the value is accepted and Traffic Server uses dynamic record
sizing (small records for roughly the first 1 MB of a response, then 16 KB records
afterward).

Actual behavior

Traffic Server rejects the value with a warning and falls back to the default (0,
which writes all available data into a single record):

WARNING: proxy.config.ssl.max_record_size - Validity Check error at line=7, col=5. Pattern '[0-16383]' failed against '-1'. Default value will be used

Dynamic record sizing is therefore unreachable from configuration, even though the
supporting code is present.

Root cause

The record definition in src/records/RecordsConfig.cc constrains the value to
[0-16383], which excludes the documented sentinel -1:

{RECT_CONFIG, "proxy.config.ssl.max_record_size", RECD_INT, "0", RECU_DYNAMIC, RR_NULL, RECC_INT, "[0-16383]", RECA_NULL}

The documentation (doc/admin-guide/files/records.yaml.en.rst) is also internally
inconsistent: it first says the value may be "between 0 and 16383," then separately
documents -1 for dynamic sizing.

Suggested fix

Decide which behavior is intended and make the code and docs agree:

• If dynamic sizing is supported: widen the validation to also accept -1, and state
  the allowed values consistently as -1, 0, or 1–16383.
• If it is no longer supported: remove the -1 description from the documentation.