### Apache Airflow version

2.6.3

### What happened

A task instance's [log_url](https://github.com/apache/airflow/blob/2.6.3/airflow/models/taskinstance.py#L726) does not contain the full URL defined in [base_url](https://github.com/apache/airflow/blob/2.6.3/airflow/models/taskinstance.py#L729C9-L729C69).

### What you think should happen instead

The base_url may contain paths that should be acknowledged when build the log_url. 

The log_url is built with [urljoin](https://docs.python.org/3/library/urllib.parse.html#urllib.parse.urljoin). Due to how urljoin builds URLs, any existing paths are ignored leading to a faulty URL. 

### How to reproduce

This snippet showcases how urljoin ignores existing paths when building the url.

```
>>> from urllib.parse import urljoin
>>> 
>>> 
>>> urljoin(
...     "https://my.astronomer.run/path",
...     f"log?execution_date=test"
...     f"&task_id=wow"
...     f"&dag_id=super"
...     f"&map_index=-1",
... )
'https://eochgroup.astronomer.run/log?execution_date=test&task_id=wow&dag_id=super&map_index=-1'
```

### Operating System

n/a

### Versions of Apache Airflow Providers

_No response_

### Deployment

Astronomer

### Deployment details

_No response_

### Anything else

This was introduced by #31833.

A way to fix this can be to utilize [urlsplit](https://docs.python.org/3/library/urllib.parse.html#urllib.parse.urlsplit) and [urlunsplit](https://docs.python.org/3/library/urllib.parse.html#urllib.parse.urlunsplit) to account for existing paths.

```
from urllib.parse import urlsplit, urlunsplit

parts = urlsplit("https://my.astronomer.run/paths")
urlunsplit((
        parts.scheme,
        parts.netloc,
        f"{parts.path}/log",
        f"execution_date=test"
        f"&task_id=wow"
        f"&dag_id=super"
        f"&map_index=-1",
        ""
    )
)
```

Here is the fix in action.

```
>>> parts = urlsplit("https://my.astronomer.run/paths")
>>> urlunsplit((
...     parts.scheme,
...     parts.netloc,
...     f"{parts.path}/log",
...     f"execution_date=test"
...     f"&task_id=wow"
...     f"&dag_id=super"
...     f"&map_index=-1",
...     ''))
'https://my.astronomer.run/paths/log?execution_date=test&task_id=wow&dag_id=super&map_index=-1'
>>>
>>> parts = urlsplit("https://my.astronomer.run/paths/test")
>>> urlunsplit((
...     parts.scheme,
...     parts.netloc,
...     f"{parts.path}/log",
...     f"execution_date=test"
...     f"&task_id=wow"
...     f"&dag_id=super"
...     f"&map_index=-1",
...     ''))
'https://my.astronomer.run/paths/test/log?execution_date=test&task_id=wow&dag_id=super&map_index=-1'
```

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

"""Custom creator for the ``note`` association proxy."""
    if isinstance(val, str):
        return TaskInstanceNote(content=val)
    elif isinstance(val, dict):
        return TaskInstanceNote(**val)
    else:
        return TaskInstanceNote(*val)
class TaskInstance(Base, LoggingMixin):
    """
    Task instances store the state of a task instance.
    This table is the authority and single source of truth around what tasks
    have run and the state they are in.
    The SqlAlchemy model doesn't have a SqlAlchemy foreign key to the task or
    dag model deliberately to have more control over transactions.
    Database transactions on this table should insure double triggers and
    any confusion around what task instances are or aren't ready to run
    even while multiple schedulers may be firing task instances.
    A value of -1 in map_index represents any of: a TI without mapped tasks;
    a TI with mapped tasks that has yet to be expanded (state=pending);
    a TI with mapped tasks that expanded to an empty list (state=skipped).
    """
    __tablename__ = "task_instance"
    task_id = Column(StringID(), primary_key=True, nullable=False)
    dag_id = Column(StringID(), primary_key=True, nullable=False)
    run_id = Column(StringID(), primary_key=True, nullable=False)
    map_index = Column(Integer, primary_key=True, nullable=False, server_default=text("-1"))
    start_date = Column(UtcDateTime)
    end_date = Column(UtcDateTime)
    duration = Column(Float)