Allow same values for depth_reference in SR as in gauges The depth_reference in a sounding result references a depth_reference of the bottlenecks reference gauge. Therefor the same values must be accepted, which means the restriction to four chars is no good. In the real world this might be something as "LDC2010", which is obviously longer.

# documentation
**/README*
**/docs
**/*.md

# backend binary
cmd/gemma/gemma

# Dependency directories
**/node_modules

# local dotenv environment variables file
client/.env.local

# Tags tables
**/TAGS