Discrepancy in the meaning of log function

[jimexist]

Describe the bug

In Postgres log is equivalent to log10 while ln exists to represent natural logarithm. Currently the datafusion function isn't consistent with this.

To Reproduce
Steps to reproduce the behavior:

run select log(10)

Expected behavior
A clear and concise description of what you expected to happen.

it should be =1 rather than >1; also there should be a dedicated ln function

Additional context
Add any other context about the problem here.