ensure concat ops are used for contains / startswith / endswith independently of datatype

[palisadoes]

Describe the use case

The existing documentation for these methods only has examples using strings. The examples are not applicable to VARBINARY columns where the queries fail.

1. ColumnOperators.contains()
2. ColumnOperators.endswith()
3. ColumnOperators.like()
4. ColumnOperators.startswith()

Databases / Backends / Drivers targeted

N/A

Example Use

The respective sections of documentation should be updated with edited text equivalent to the suggestions below:

ColumnOperators.contains()

• When byte strings are stored in the database columns (eg. VARBINARY), you should use standard SQL wildcards with the like() method to represent .contains():

stmt = select(sometable).where(
    sometable.like(func.concat(func.concat('%', 'foobar'.encode()), '%'))
)    

Using .contains() with the same concatenations will produce an equivalent result.

ColumnOperators.startswith()

• When byte strings are stored in the database columns (eg. VARBINARY), you should use standard SQL wildcards with the like() method to represent .startswith():

stmt = select(sometable).where(
    sometable.like(func.concat(func.concat('foobar'.encode()), '%'))
)    

Using .startswith() with the same concatenations will produce an equivalent result.

ColumnOperators.endswith()

• When byte strings are stored in the database columns (eg. VARBINARY), you should use standard SQL wildcards with the like() method to represent .endswith():

stmt = select(sometable).where(
    sometable.like(func.concat(func.concat('%', 'foobar'.encode())))
)    

Using .endswith() with the same concatenations will produce an equivalent result.

Additional context

N/A

[zzzeek]

So I dont think a document here is sufficient, because people tend not to find docs like these.

What I would prefer is:

1. we figure out what these operators should do when passed a bytestring and do that
2. we have it raise an error

1 is likely preferable

[sqla-tester]

Mike Bayer has proposed a fix for this issue in the main branch:

use concat() directly for contains, startswith, endswith https://gerrit.sqlalchemy.org/c/sqlalchemy/sqlalchemy/+/3996

[sqla-tester]

Mike Bayer has proposed a fix for this issue in the rel_1_4 branch:

use concat() directly for contains, startswith, endswith https://gerrit.sqlalchemy.org/c/sqlalchemy/sqlalchemy/+/3997