Add condition asserting str is in Message.text (#335)

# Description

- Function has_text() added. Checks the 'text' field of last_request(),
if specified text within 'text' field, returns true.
For such a task it's quicker than regexp condition and has less syntax
bloat than exact_match() would have.
This also makes checking telegram callback data easier since it is saved
in the 'text' field: has_text(callback_data).
 - All relevant API reference / tutorials / guides updated.
By that I mean all 'exact_match(Message("Some message"))' was changed
into 'has_text("Some message")'.
 - All relevant references in the codebase updated.
- Tests added, but I'm not sure I did it right. I changed some
exact_match() uses to has_text() there. Well, vim did it, and now I'm
thinking it's maybe preferable, actually.
# Checklist

- [x] I have performed a self-review of the changes
- [x] Check if tests are done right (poetry has no issues, I mean if
exact_match() should return instead of has_text())
# To Consider

- Consider if exact_match() could somehow be used in tandem with
has_text() in the tutorials. It's a part of functionality that new users
can't really see now, since it's rarely used (mostly in telegram
tutorials).

---------

Co-authored-by: Roman Zlobin <[email protected]>

dff/script/conditions/__init__.py

@@ -2,6 +2,7 @@
 
 from .std_conditions import (
     exact_match,
+    has_text,
     regexp,
     check_cond_seq,
     aggregate,

dff/script/conditions/std_conditions.py

@@ -50,6 +50,22 @@ def exact_match_condition_handler(ctx: Context, pipeline: Pipeline) -> bool:
     return exact_match_condition_handler
 
 
+@validate_call
+def has_text(text: str) -> Callable[[Context, Pipeline], bool]:
+    """
+    Return function handler. This handler returns `True` only if the last user phrase
+    contains the phrase specified in :py:param:`text`.
+
+    :param text: A `str` variable to look for within the user request.
+    """
+
+    def has_text_condition_handler(ctx: Context, pipeline: Pipeline) -> bool:
+        request = ctx.last_request
+        return text in request.text
+
+    return has_text_condition_handler
+
+
 @validate_call
 def regexp(pattern: Union[str, Pattern], flags: Union[int, re.RegexFlag] = 0) -> Callable[[Context, Pipeline], bool]:
     """

tests/script/conditions/test_conditions.py

@@ -21,6 +21,11 @@ def test_conditions():
     assert cnd.exact_match(Message())(ctx, pipeline)
     assert not cnd.exact_match(Message(), skip_none=False)(ctx, pipeline)
 
+    assert cnd.has_text("text")(ctx, pipeline)
+    assert cnd.has_text("te")(ctx, pipeline)
+    assert not cnd.has_text("text1")(ctx, pipeline)
+    assert cnd.has_text("")(ctx, pipeline)
+
     assert cnd.regexp("t.*t")(ctx, pipeline)
     assert not cnd.regexp("t.*t1")(ctx, pipeline)
     assert not cnd.regexp("t.*t1")(failed_ctx, pipeline)